Sanjay ilovecold at gmail.com
Sun Apr 18 10:53:54 EDT 2010

We use our PCs pretty much every day, but a worryingly large amount of that time
is spent troubleshooting computing headaches.  Rick Broida and Rosemary
Hattersley address some of the most frustrating problems a PC user can face

Here's a poser for you: when was the last time you went a whole day without
touching your computer?  Access to the web is now viewed as a right, not a
privilege, and the provision of broadband-grade internet access is a national
priority - but where would either of these be without the humble PC?  Whether
it's serving up web pages, music, photos, TV and videos or helping you make
sense of the household accounts, the personal computer is an invaluable tool and
an established source of entertainment.

Given its myriad roles and boundless capabilities, it's little wonder that
this complex invention doesn't always perform exactly the way it should.  In
fact, the surprise is that PCs don't go wrong more often.  When things do go
awry, you often write or email to tell us, sometimes with an anecdote about
misbehaving components or a tale of woe about how hard it is to get things
fixed.  Many times, it's because you're keen to roll up your sleeves and try
to fix things yourself, and need some pointers.

Each month we bring you several pages of Helproom Q&As - queries and taxing
problems you've written in to tell us about in the hope that we can help
resolve them.  We print both the query and our suggested fixes in
the belief that issues afflicting one reader are highly likely to have puzzled
or aggrieved others too.  Some are very specific issues: one reader recently
found his laptop picking up the frequency of American overseas radio broadcasts.
Other queries, however, are all too familiar.  Our inbox and our online forums
are certainly never short of pleas for help or commentary about the quirks of
day-to-day computing.

Every so often, we like to take a step back and see what sort of computing
issues are causing the biggest headaches, and what we can do to alleviate them.


Some of the most troublesome computing issues rear their heads when you first
switch on your PC.  Whether the power button elicits no response or you get a
screen full of error messages once you've booted into Windows, there's
nothing worse than everything going wrong before you even begin.

Failure to launch 

First off, let's look at why a PC might not start up in the first place.  If
you can't hear the hard drive spinning or the fan whirring into life when you
press the power button, the chances are the power supply unit (PSU) has gone
west and needs to be replaced.  Before you rush out and buy a replacement,
though, check it's not the electrical socket at fault as it's possible
you've fused it.  Plug in a device you know works to rule this out.

If you've recently upgraded to a more powerful graphics card, it's likely it
draws far more power than its predecessor, in which case you'll certainly need
to replace the PSU.  For advice on which, see our group test and buying advice
at tinyurl.com/PSUtest.

If the PC sounds as though it's going to power up but nothing appears
onscreen, check that the monitor is properly connected and that it works.  Try
an alternative power cable or connecting cable.  If the screen works but Windows
doesn't complete its boot-up routine, you probably need to replace the Cmos
battery.  Consult the motherboard maker's website for advice on how to reset
its jumpers.

Other potential culprits include the graphics card and a faulty RAM module.  The
free MemTest86 ( memtest86.com) will help you establish whether the latter is
the case.  In most cases, though, Windows or a conflicting piece of code are
more likely to prevent your PC booting up.  Try restarting your PC and booting
into Safe Mode.

Slow startups 

We've covered the issue of unacceptably slow startups many times before.
While Vista users have largely got used to the tortoise-like progress of their
shiny operating system (OS) as it labours into view, Microsoft bloat isn't
necessarily at the heart of every slow startup.  The programs you install and
the applets intended to improve your web experience are just as likely to be at

The secret is to deactivate those that don't need to launch the moment Windows
fires up.

To see what's set to load when you boost up your PC, go to Start, All
Programs, Startup in XP.  To delete a non-essential item from this folder,
right-click it and choose Delete.  To get rid of it entirely, go to Add/Remove

Another option: in Vista or Windows 7 go to Start, Run, type msconfig and press
Enter.  Click on the Startup tab and untick any unwanted programs.

If you merely want to postpone some apps auto-starting, you need Startup Delayer
( bit.ly/1FCBg7).  This free app gives you control over which program or service
loads and in which order, so they aren't clamouring for the same processor
cycles.  Adjust the slider next to each item to set how long Windows should wait
before loading it.

Untidy system tray or Start menu 

Telltale signs of a clogged-up system include a system tray full of icons and
regular notifications emanating from it, plus a Start menu full of apps with
unfamiliar names.

Microsoft has recognised the extent to which PC annoyances stem from the system
tray or Start menu.  Windows 7 replaces the Quick Launch function with a Jump
List that lets you preview documents and programs and fire up frequently used
items on demand, leaving the Start menu uncluttered.

Get rid of ghost drivers 

If your PC is more than a couple of years old, it's possible that Windows is
loading up drivers from hardware you no longer use - scanners, printers or
external hard drives you've long since retired.  To check whether this is the
case and to prevent it happening, go to Device Manager and press Windows, R to
open the Run box, type cmd then hit Enter.  At the command prompt, type set
devmgr_show_nonpresent_devices=1 a display all services and drivers that load.

Press Windows, R again, type devmgmt.msc, then hit Enter.  In the Device Manager
window, choose View, Show Hidden Devices.  Click the plus sign next to each
branch to examine the drivers.  Devices that aren't connected appear with a
pale version of the icon.  If you come across a device you no longer use,
right-click it and choose Uninstall.

Maximise performance 

Once you've banished hanger-on apps, you can assess whether your PC is
fulfilling its potential.  If it's a Vista or Windows 7 machine, you'll be
able to get a ready idea of how well it's doing by going to the Windows
Experience Index screen: go to Control Panel and type experience into the search
field, then click either option that appears.

This screen rates general, graphics and network connection performance against a
database of other computers running the same OS, and identifies areas of your
hardware setup for possible improvement.

For a more in-depth look at how well your PC is working, our own diagnostic
tool, PC Performance Monitor ( bit.ly/3IDbU9) is worth trying.  You need to be
logged in to the PC Advisor website and set aside a few minutes for the tool to
make its assessment.

Some of the most effective tools to ratchet up performance involve Registry
tweaks and cleaners, although regularly archiving and offloading files from your
primary hard drive and ensuring you've got enough RAM will also help.

Regular readers of our Helproom pages will be familiar with CCleaner, a useful
utility that cleans up your PC while removing outdated Registry entries.  Other
effective tools include Uniblue RegistryBooster 2010, reviewed at

Resolve startup error messages 

Here's a fun way to start the day.  You fire up your PC and see an Internet
Explorer window that declares: 'Cannot find "File:///".  Make sure the path or
Internet address is correct.'

Stuff like that can be seriously annoying; one reader was aggravated enough to
send us an email about it.  We reckon Windows was looking in vain for a leftover
file related to a recent installation or uninstallation.

A startup monitor tool shows everything attempting to run during the boot
process so that you can determine which IE-related item is the offender.  Run
the free utility Autoruns ( bit.ly/s7 grams 3Q), click the Logon tab and look
for entries that point to iexplore.exe.  If you find one, untick its box and

Alternatively, Windows' built-in MSconfig utility may come to your aid.  Click
the Startup tab and check the Command column for entries containing
iexplore.exe.  Deselect any you find, press ok and reboot your PC.

Shut down - don't standby 

If the power button light continues to blink even after you've shut down your
computer, it's likely to have gone into standby mode rather than fully
powering down.  There are two easy ways to address this.  First, you can click
the Start button, move the cursor over the arrow at the bottom-righthand corner
of the Start menu and click Shut Down.  (The power button to the right of the
search box in Vista is actually a standby button.)

The second option is to change the function of your laptop's power button so
it actually shuts down Windows.  In Vista, click Start, type power, and click
Power Options.  Now click 'Choose what the power buttons do' and make the
necessary changes.  Click 'Save changes' to implement them.

Fix unwanted Windows reboots 

You step away from the PC for a while and, when you come back, all your windows
and work are gone.  Why?  Because Windows downloaded some updates and took it
upon itself to reboot without your permission.

Thankfully, the fix is very easy.  In Vista, click Start, type Windows Update
and press Enter, then click the Change Settings option on the left.  In XP, head
to the Control Panel and seek out Windows Update.  Clicking on this takes you to
a browser page where you can check for available updates and specify how and,
crucially, when these are applied.

Press Custom and adjust what is automatically installed.  The box on the right
lets you specify a time of day for updates to be applied, such as 3am.
Depending on the options you've selected, Windows may still nag you about
installing updates, but at least it won't reboot without permission.

Hardware fixes 

Due to the modular and customisable nature of PCs, the precise components that
control the logic board, processor, graphics and visual output will differ for
almost every person reading this guide.

Two PCs with the same product code may have subtle differences - a Sapphire
ATI Radeon graphics card rather than a Gigabyte one, for example.  And once
you've taken possession of your PC, you load it up with software and files,
and switch the keyboard and mouse for ones you find more comfortable or visually
appealing.  These accumulated alterations make your PC unique.

That's why it's useful to take an inventory of precisely what's on your
PC.  The Belarc Advisor from belarc.com does just this; it also lists outdated
drivers and hotfixes you've skipped.  If you missed our guide to firmware
updates, read it at bit.ly/PiG5I.

Common complaints 

Some hardware issues are common for all products of that type.  For example,
diagnosing a dodgy DVD drive or establishing whether your hard drive is about to
die a death is fairly straightforward, regardless of its brand.  In fact, the
most common complaint at PC Advisor Towers across Macs, PCs, laptops and desktop
machines of differing brands and proximity to retirement is that the DVD drive
no longer works.

In a surprising number of cases, updating the driver for the drive in question
is the standard fix.  You'll need to know the make and model number, which is
where that Belarc tool we mentioned comes in.  It's also worth running a web
search for the model in question, as some drives have known problems that mean
you're better off replacing the drive than updating it.

You should also check whether Windows thinks the drive is working correctly by
going to My Computer, looking for the drive's icon and right-clicking to
establish its status.  If Windows says the drive is working properly, the discs
you're trying to read or burn may be faulty or of a type the PC can't read.

If, however, your DVD drive is no longer being recognised by Windows, you may
need to update the Bios.  You should also establish whether it's seen by the
Cmos - if not, the connecting cable may have come loose, causing it to be
recognised no longer.

Loose components or connections 

And it's not just cables that come loose: it's not uncommon for PC
components to drop out of your arsenal.  With new items such as upgraded RAM and
graphics cards, it's one of the first things you should check.

But before you unplug the computer and start investigating its innards, ground
yourself by touching metal.  Move the PC to an uncarpeted area before opening
the case.  An antistatic wrist strap is also a good idea.  Open the case and
identify the problem part, checking for anything that looks as though it may be
amiss.  If that new graphics card is sitting at an odd angle, for example,
it's unlikely to be working the way it should.

To check PCI cards, unscrew the fixings on the side of the PC chassis for each
one in turn, then lift it straight out of its slot.  In the case of a graphics
card, there's probably a plastic release tab or retaining lever.  Handle the
card by its edges only.  Now clear the slot it fits in before pushing the card
straight back in.  It should slide down without any rocking, landing with a
satisfying thunk.

Similar reseating advice applies to RAM modules.  Most motherboards release
their RAM modules if you pull apart levers on the modules' edges.  Lift the
RAM straight up and out, leaving the levers in the open position.  Reinsert the
RAM module by pushing it straight down, again without rocking.  The levers will
snap to their closed position.

Be gentle; don't force any PC parts. 

Close the case and try rebooting the PC.  If it still won't start, open it
again, then unplug and reconnect all the internal cables.  Finally, try
connecting only the most basic cards and components, such as the original RAM.
If this works, gradually reinstall parts to establish what's malfunctioning.

Unclog your ports 

Over time, ports on your electronic equipment can get clogged with dust and
other debris.  If you're having trouble getting USB or other devices to work
with your PC, cleaning any grime from the connecting ports is a sound first

Turn off your PC.  If you can see the port is severely clogged, try a toothpick
to clean out the gunk.  Be gentle, though: Ethernet, serial and other
connections rely on fragile pins, so try to move in and out on the same path
instead of swishing around.

For less sticky situations, use a can of compressed air (actually pressurised
gases) to blast out loose bits.  You should be able to get hold of one of these
at Maplins or another hardware or computer shop for less than ukp10.  This works
best if you fire at the target in short bursts.  Complete the cleaning process
with a cotton swab dipped in rubbing alcohol or electronics cleaner.  Leave the
device turned off for a few hours to dry.

Unstick a sticky keyboard 

Another recommended spring-cleaning task is to de-gunk your keyboard; if you
munch toast while scanning online news headlines, there's sure to be evidence
in your keyboard.  Cleaning your keyboard may not prevent the PC going wrong,
but it will definitely make for a healthier working environment.

Spillage clean-ups 

The other big issue affecting computer keyboards is the classic spill.  As we
all know, liquid and electronics aren't intended to mix.  If you do have an
accident, act promptly.  Power down the PC, unplug it from the mains and
disconnect the keyboard.  Turn it upside down on a draining board or suitable

If we're talking about a laptop rather than a desktop PC, time is even more
critical.  Conductive liquids cause most of the initial damage.  Immediately
unplug the laptop and pull out the battery.  Don't bother closing programs or
saving data.  Disconnect any hard drives and remove media cards.

Carefully turn over the laptop, ensuring the liquid doesn't go anywhere near
the screen.  You want to remove as much liquid as possible, but you need to
ensure it doesn't spread to other parts of the machine.  If possible and
necessary, remove more parts.  Unscrew the outer case and remove the plastic
shell to expose the internal circuits.  Disassemble parts even further,
separating individual components to help them dry.  Do as much of this as you
are comfortable with.

A good local laptop repair shop may be able to offer yet more help, but your
speedy actions will make the most difference.

Once the laptop has dried out a bit, you may need to clean the affected parts
with electronics circuit cleaner.  You won't need to do this if you only spilt
a few drops of water.  If the spill was more than 100 millilitres or something
sticky or corrosive, grab the circuit cleaner and set to work with rubber gloves
in a ventilated area.

Now wait for your system to dry.  Leave the laptop disassembled or open and
upside down for a couple of days.  Wait even longer if possible.  Do not be
tempted to use a hair dryer to speed up the process.  Instead, leave the laptop
in a warm room, next to a window sill or in another dry location.

Reassemble the laptop and turn it back on.  If the keys are sticky, turn the
system off and disassemble the keyboard for fine cleaning.  If the laptop
won't turn on, your hard drive may still work.  Remove the drive, put it in
another case or hook it up to an adaptor, and connect it to a different PC.
Your last resort is a data-recovery service such as Ontrack (ontrack.co.uk).

Blow away the cobwebs

Dust is the enemy of your PC, since grime can clog the fans that keep internal
parts cool and restricted airflow can cause them to overheat.  A regular
spring-clean is a good preventative move.  Shut everything down and unplug all
cables.  Touch a metal part of the case and unplug the power cable to discharge
any potential static externally, instead of damaging electrically sensitive
components.  Wear shoes and work in an uncarpeted room.  You may also want to
place a layer of rubber (such as mouse pads) between the PC and your worktable.

Wear an antistatic bracelet, and connect it to a metal part of the chassis.Open
the PC case to clear out any grime.  Many cases have side doors held in place by
a single Phillips-head screw or a thumbscrew; consult your manual for specific
directions.  Pull out any loose obstructions.  Now use a can of air to blast
anything else away and out of the PC.  Blow grime up and out of the case if
possible, but focus your attention on clearing clogs at vented areas.  Blow
through gratings, and blow from inside the PC, out through the power supply's
fan, until you no longer see any dirt being cleared away.

While you're inside, make sure that internal cables are clear of the vents.
Use cable ties to fix them to the sides.  Reclose the case, and reconnect
everything.To slow future dirt accumulation, keep your PC off the floor, since
that's where most grime originates.  Repeat the cleaning process annually,
especially if you have pets.

Unstick a stuck pixel

LCD monitors contain millions of pixels, each composed of three sub-pixels: red,
blue and green.  When all three are on, a pixel looks white.  Other combinations
create other colours.  A pixel can become stuck showing only one hue.  But you
can fix this.

Determine whether the pixel is just stuck or completely dead.  If it shows only
black, it's probably inoperable.  If it shows a solid, it may simply be stuck
and you may be able to 'shock' it back into operation.Spray your screen with
a few blasts of compressed air, then wipe it with a scratch-free cloth and
screen cleaner.  Check your PC is outputting in your LCD's native resolution
so you can identify pixels more easily.

Open Start, Control Panel, Display, click the Settings tab and adjust the
resolution.  Install UDPixel (udpix.free.fr/) to identify and fix the problem
(you'll need to grab the .NET framework from bit.ly/4pzvTf).  In UDPixel,
increase the Run cycle option to 4 secs and click Run cycle.  The display will
cycle through red, green, blue, black, white and yellow.  A stuck pixel should
be visible against every hue but the one it's stuck in; unchanging dots are
problem areas.Click Start and a small, 5x5-pixel box will appear.

Reposition the box around the stuck pixel, then wait 15 to 20 mins.  Click Reset
to turn it off.  Repeat the colour cycle to see whether the pixel has cleared.If
the problem persists, check your warranty.  If you can't get a replacement,
try applying direct pressure - it's been known to salvage a few screens.
Wrap the tip of a PDA stylus or similar object in a scratch-free cloth, then use
UDPixel to find the problem.Align the stylus directly over the pixel.  Turn off
the screen and gently apply pressure for 5 to 10 secs.  Alternatively, try
wrapping the rounded, plastic end of a marker pen in a scratch-free cloth and
gently tapping the afflicted area a few times.


One of the biggest headaches for PC users updating their machines - especially
if they're making the move from one operating system to another - is
ensuring they can still run the programs they depend on.

>From XP to Vista 

A major criticism of Windows Vista when it launched was that too little had been
done to ensure software and hardware written for Windows XP would be able to run
on the new version of the OS.  While the lack of signatures verifying
compatibility and giving the Microsoft blessing was understandable, many
upgraders felt the sheer number of programs that simply didn't work in Vista
was unforgivable.

Most compatibility issues were eventually ironed out, usually by third-party
software makers writing updated drivers for their hardware.  Microsoft also
introduced a Compatibility Mode for Vista for any programs that couldn't
natively run under this version of Windows.

If you've encountered a program that you can't use in Vista, go to Control
Panel and click the Programs tab.  Choose 'Use an older program with this
version of Windows' and follow the instructions in the wizard.

In some cases, you can change the way an installed program runs by
right-clicking on its icon to bring up its Properties dialog box.  Choose
Compatibility to make it use the Compatibility Mode.

The major exception to all this good news concerns games.  If you've got a
cupboard bursting with games you've enjoyed playing on your XP machine, and
want to know whether they're likely to run under Windows 7, we suggest you
Google each game that's important to you.

If a game runs in Vista then it should be fine in Windows 7, but there are
plenty of instances of XP games not running in Vista.

>From XP to Windows 7 

Since upgrading from XP to Windows 7 involves an 'advanced' (complete, in
other words) reinstallation of Windows rather than an incremental or in-place
one (which you can perform when upgrading from Vista), you want to be sure of
what will run before you make the upgrade.

If you've got a massive library of software you can't replace or replicate
without major expense, dual-booting your PC may be the best bet.  You'll need
to use a partitioning tool such as PartitionMagic for XP (Vista has its own) and
an ISO creation tool such as Imgburn.  You'll need to make a comprehensive
system, files and settings backup.  Given the vast storage on today's PCs,
however, it's a very workable option.

Unfortunately, Microsoft has elected not to provide an XP Compatibility Mode for
consumers buying the newest version of Windows.  You need to have the
Professional Edition or Ultimate Edition of Windows 7 if you want to be able to
continue using XP programs that wouldn't otherwise work in Vista or Windows 7.
Type compatibility into the search box on the Start menu to bring up the Program
Compatibility tool.

UsingG PERIeriPHERherALSs with 7 

Windows Vista and Windows 7 share almost identical code, so you shouldn't have
problems with any peripheral you were successfully using under the older OS in
the new one.  However, it's always worth checking for driver updates if
you're having issues with a peripheral.  In fact, Windows 7 users can look
forward to far better hardware management and comprehensive management and
status tools, thanks to a new feature known as Device Stage.  Microsoft made the
code for this available to hardware manufacturers well in advance of Windows
7's launch so they could write apps and additional features for when their
devices are plugged into a Windows 7 PC.

Keep safe online 

Web access is something we all take for granted - an entire working day can
depend on it, while our social lives and entertainment needs are increasingly
served by our ability to chat, connect and plan using the web.

But being connected - to other devices and to the web - can bring with it
some degree of danger, which explains the need for antivirus apps and the
preventative measures Microsoft introduced in the form of UAC (User Account

The latter proved a classic case of the cure being worse than the illness, but
there are ways to take back control of your PC without switching off UAC
completely.  And in Windows 7, more granular controls and a 'trusted' group
of networked printers, PCs and other devices means you can create HomeGroups,
allowing you to log in and connect with other members without further ado.  If
only non-Windows 7 PCs could join in.

Tame UAC (but keep its benefits) 

Microsoft has done much to improve the security of its desktop operating system
in the past five years, but it took until Windows XP Service Pack 2 for it to
start getting it right.  Unfortunately, in Windows Vista it went too far the
other way, with the draconian UAC actively preventing you from installing
programs or performing certain actions without confirming that you meant to.

Almost everything you try to do in Windows Vista results in a warning message
advising you against it, or telling you to think carefully before proceeding.
Sometimes UAC pops up a warning even though it's a Microsoft app or a Windows
action that prompted it to leap into defensive action.

TweakVI, an invaluable set of tweaking tools for Windows Vista users, offers
ways of taming UAC so it takes a more laid-back approach.  Use this rather than
switching off UAC completely, since this would negate the benefits of having it
at all.

In Windows 7, you can ensure you rarely see the UAC warning box.  Go to Start,
Control Panel and bring up the Action Center (Windows 7's equivalent of the
Security Center).  Click Security to adjust UAC's behaviour.  The slider bar
allows you to have UAC leap in only if it detects an action you didn't
deliberately initiate.

On the subject of the Action Center, it's worth pointing out that this central
location also provides a helpful overview of your firewall and other security
apps.  Use it to manage notifications and turn off anything that's bugging you
in the taskbar.  To do this, go to the Windows 7 Start menu, type Action, click
the Action Center option and, under the Settings menu, deselect the
notifications relating to those maintenance and security tasks that you don't
wish to be nagged about.  Click ok to apply the changes.

Banish fake security apps 

The past 18 months have seen a rash of fake security programs doing the rounds.
These offer to check your PC for spyware and other malware of one kind or
another, magically find some (having installed their own malware in the form of
a Trojan) and then demand money to 'upgrade' to the full version of the
supposed security program.

The situation was exacerbated by scammers posting cogent-sounding online
reviews, purportedly written by respected magazines and websites, that served to
make their spurious products sound legitimate.  In fact, it's increasingly
hard to tell whether an antivirus program is to be trusted, which is why so many
readers and forum members have been in touch asking how on earth they can get
rid of the likes of Antivirus 2009 and Total Security 2009.

In the case of Antivirus 2009, the most successful and prevalent of the fake
antivirus programs, you could try an antispyware program such as the well-known
Spybot Search & Destroy ( spybot.com) or run Microsoft Security Essentials.

If you can't get rid of the unwanted app using these, try the $39 XoftSpySE
(download it from tinyurl.com/pareto).  You should first use the Add/Remove
Programs tool in XP (known as Uninstall Programs in Vista or Windows 7), then
restart the computer in Safe Mode - press F8 when the boot screen appears.
>From here you should be able to run the antispyware program and have it excise
any remaining nasties.

Defuse antivirus conflicts 

Perhaps because there have been so many stories of Trojans, worms and viruses,
some people have tried to double up on their defences by installing more than
one security program - but this is dangerous.

You can have a firewall and an antispyware program running alongside an
antivirus program, but you shouldn't attempt to have more than one of each
product type.  In the case of antivirus applications, they will compete for
attention and you may end up in an endless cycle of, say, Norton trying to
prevent Trend Micro running.  Usually, one app will identify the other as
possible malware and quarantine it, effectively neutralising its ability to act.
You think your PC is doubly protected, while all the while battle is raging and
other unusual activity of a more sinister kind is being missed.

As with the advice related to fake AV apps, a visit to Safe Mode is required,
since the standard method of uninstalling and reverting to the relevant System
Restore point may be seen by the security apps as attempts to circumvent their

Check carefully for remains of the app - very often they will try to autoload
at startup and may have additional shortcut entries in the Startup menu.  You
need to clear your PC of these too.  Several restarts may be required before
you've completed the clearout process.  Ensure you rescan your PC when
you've finished and download any updates to the antivirus software you decided
to keep.  A PC's antivirus program is useless unless it's up to date - and
updates can be daily or even more frequent.

Get better connected 

The final two bugbears we'll address in this feature concern connectivity: the
web sort and the network sort.  The first one is an all-too-common scenario -
one minute you're surfing the web, the next you have no connection.

While it's possible the internet or your ISP has gone down, it's much more
likely that you need to release your current IP address and acquire a new one.
The process for re-establishing your web connection is the same for all versions
of Windows.

Click Start, Run and type cmd in XP or simply type cmd into the Search box in
Vista or Windows 7.  When the command prompt appears, type ipconfig to bring up
the current IP address, subnet mask and default gateway.  You need to flush out
the current IP address.  Type ipconfig/release to instruct the DCHP server to
forget the details it holds.  Type ipconfig/renew to acquire a new dynamic IP
address and get back online.

Incidentally, if you suddenly find yourself unceremoniously dumped offline on
your smartphone, a similar principle applies.  Go to the Settings menu in your
iPhone or other Wi-Fi-enabled handset, instruct the device to 'forget this
network', toggle the Wi-Fi off and then on again if you wish to track down an
alternative network.  This can be particularly useful in locations where
there's a commercial Wi-Fi hotspot vying for your business and knocking out
the 3G connection you were already enjoying.

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