How to reinstall Windows

The trick is as follows:

The process of reinstalling Windows on your computer is simpler than you might think.

The very idea can often induce a mild sense of panic, but the benefits of reinstalling Windows far outweigh any perceived risks, particularly as you can eliminate those dangers simply by making sure you back things up as you go.

Reinstalling Windows offers a number of benefits. It can revive a sluggish system by clearing out all the clutter and letting you start from scratch.

You'll be amazed at how quick your PC suddenly feels, and it'll be more stable too, with corrupt files and problematic programs removed from the equation. In many circumstances it can also clean your computer of malware, although it's important to note that this isn't guaranteed.

There are three different levels of reinstalling you can perform depending on how far you want to go, and in this feature we'll cover them all – from a quick over-the-top reinstall to try and fix minor problems to a full-blown reorganisation of your hard drive, complete with formatting and fresh installation.

Whatever ails your computer, there's a reinstall solution to help fix it.

If you're reinstalling Windows because you think your system needs a quick refresh, then a repair installation is worth considering. The whole process takes less than an hour, and basically installs a fresh copy of Windows over the top of your existing, jaded copy, so that programs, settings and data remain intact.

There are two ways to perform a repair install: if your copy of Windows was pre-loaded by your manufacturer, follow its instructions for a system recovery, choosing 'non-destructive' when prompted. This may involve recovery discs, but in most cases can be done by rebooting and before Windows loads, pressing the key to access recovery options.

Not all manufacturers provide a non-destructive option – if the only options you can see involve partitioning, formatting or wiping your existing installation, you'll have to jump to the next section and perform a full-blown reinstall instead.

If you installed Windows from an installation disc, then the process is a little more complicated. If you've installed any Service Packs since Windows was first installed, then these will need to be removed as the installation disc will detect a 'newer' version of Windows and refuse to install over the top of it. If you're unable to remove the Service Pack or you're unable to boot into Windows at all, then you'll need to perform a full reinstall instead.

NOTE: Commenter badvok66 rightly points out that if you have apps that require authorisation or authentication (such as iTunes, some anti-virus programs or Adobe Creative Suite) then you ought to deactivate these before reinstalling your system to prevent any problems when reactivating.

Perform the installation

The step-by-step guide below reveals how to perform a repair installation in Windows 7 and Windows Vista. Windows XP users do things differently: start by rebooting with the Windows XP CD inserted.
Press any key when prompted – if you get a message about Windows not being able to recognise your drive, you'll need SATA drivers on a floppy disk (check the manufacturer's site for a make-disk utility). Then restart the process, pressing F2 when prompted to load the drivers.
When the Welcome screen appears, don't press R – instead, press Return to set up Windows as directed. Press F8 and Windows will scan for your existing installation. Make sure it's selected and then press R to repair it.
Windows XP will now delete all system files and copy replacements from the installation disc. Setup will then initialise and save your configuration, then reboot. Ignore any request to boot from CD.
When prompted for your language settings click Customize – set both options to English (United Kingdom), then switch to the Advanced tab and do the same. Click OK > Details. If it's present, select English (United Kingdom) – United Kingdom from the menu or click Add to pick it from the list.
Once done, pick the US entry and click Remove followed by Apply, then click OK twice. Click Next, then enter your product key – you should find this with your installation disc. Then click Next.
Once complete, Windows XP will restart – click Next at the first screen, opt whether or not to register and click Next again followed by Finish.

Post repair steps

Once the repair process is complete, you should find yourself back at your desktop. Your programs, files and user settings should be intact, although some things, such as System Restore points, will be lost. Some programs may also stop working – try installing the program over the top of itself to resolve these lingering problems.
All that's left to do is to bring your PC back up to date. Open Windows Update to check for and install updates – you may have to repeat the process a few times, rebooting Windows when prompted, before it finally tells you everything is current. A repair install can resolve many niggling stability issues, but if the problems continue it's time to perform a complete reinstallation.

Repair installation: Get a new PC in 30 minutes! (Win Vista/7)

1. Remove service packs

If you've installed a Service Pack after Windows was first installed or loaded on to your computer, you'll need to remove it first. Open the Programs and Features Control Panel and select View installed updates. Scroll down, select Service Pack for Windows and click Uninstall to remove it.
2. Start repair process

The repair installation process must be run from Windows itself – boot into Safe mode if necessary to start it. Pop your Windows disc into the drive and if the Autoplay dialogue box appears, click Run setup.exe. If it doesn't appear, click Start > Computer and double-click the DVD drive icon.
3. Get updates

Click Yes followed by Install Now to start the process. When prompted, click Go online to get the latest updates for installation (recommended) and wait for them to be downloaded. Once done, the process will automatically restart.
4. Choose upgrade installation

Read the licence, then tick I accept the license terms before clicking Next. Windows Vista will ask for your product key (Windows 7 will skip this step), then at the next screen choose Upgrade. Now wait while the compatibility check is performed.
5. Make a cup of tea

Once complete, Windows will install over the top of itself, following a similar – but not identical – process to a fresh install. It will restart several times during the process, but can be safely left to its own devices. Expect this to take half an hour or so.
6. Complete repair process

When prompted, enter your product key and click Next. Choose Use Recommended Settings, then work your way through the rest of the set-up wizard verifying your time zone and network settings – click Skip to ignore any irrelevant parts.