This is how to reinstall Windows 7 from DVD. However, some PCs allow you to reinstall Windows from a separate recovery partition on your hard disk and, in that case, you should follow the manufacturer’s instructions. Alternatively, if you’ve lost your Windows 7 disc and your PC doesn’t have a recovery partition, take a look at our guide to reinstalling Windows without a disc.

If you're reinstalling Windows on the same hard drive as it's currently installed you have two choices: Upgrade or Clean install. The former will keep all your stuff but may not fix a problem you're having, while the latter will wipe your hard drive and you'll lose all the data from that partition (or the whole drive if there's only one partition on it). Make sure you've backed up everything you don't want to lose.

Also, don't forget you’ll need to activate Windows after installation using the product key (the five groups of five characters shown next to 'CD Key:' in the image below) so make sure you can find it on a Microsoft sticker somewhere on your PC. If there’s no sticker or it’s illegible, you might be able to get it running Magical Jelly Bean Keyfinder on the PC in question. (When you install it, be careful not to also install the optional search bar.)

With that done, shut down your PC put the Windows disc in the CD/DVD slot and start it up. All being well, it should boot from this. If it boots to Windows normally, you’ll have to use the BIOS menus to make your PC boot from a disk – see How to enter the BIOS for instructions.

When you've made the computer boot from the DVD or USB drive, Windows Setup will start and on the first screen you need to specify your preferred language, time and currency format, and the nationality of your keyboard. Just follow the on-screen instructions.

Next you’ll now be asked “Which type of installation do you want?” and both options will be explained. Choose the “Custom (advanced)” option will take you back to the way your PC was when it left the factory. (Note that you could try the Upgrade option to reinstall Windows "over the top" of your existing installation to see if it fixes a particular problem you're having. This will keep all your files, programs and settings intact.) We'll show you how to to a clean install here.

Next you’ll be asked “Where do you want to install Windows?”. Sometimes just one partition will be shown, in which case just click on Next. If multiple partitions are displayed, select the first primary partition (usually the largest) before clicking on Next.

Windows 7 will now be installed and progress will be reported in the list of actions and the progress bar. This could take some time. Often it’ll seem that the installation has got stuck in the “Completing installation” phase so be patient and don't turn off your computer.

Finally you’ll be guided in setting up a user account. Also, you’ll need to provide the product key that you identified earlier. This will be used later when there's an internet connection to activate the new installation of Windows.

Follow the instructions to select security options (we suggest accepting the default setting), the time and date format, and perhaps to connect to a wireless network and join a Homegroup if these are detected.

Windows will now start but the desktop will look different and rather empty. Your next job, therefore, is to re-install the various applications that you use on a regular basis.

Now go to Device Manager – search for it in the Start menu – and check that drivers have been installed for all the hardware. If you see and devices with an exclamation mark, go to the manufacturer’s website and download the latest versions. You should find the appropriate drivers by using your laptop’s exact model code; for a PC, you’ll need to know the motherboard make and model, and the model numbers of other key components such as the graphics card.

Even if you see no problems, it's worth installing manufacturer-specific drivers (rather than the generic Microsoft drivers which Windows will have installed) for components such as the graphics card, motherboard chipset, laptop touchpad etc.

Plus, there may be manufacturer utilities (especially for laptops) which won't be reinstalled with a ‘clean’ copy of Windows. For example, some laptops have utilities which prevent the battery charging to 100 percent, prolonging its life.

Now, you can copy all your files back onto your PC that you backed up at the start. You’ll probably also want to select your favourite wallpaper and make all the other changes necessary to customise your PC the way you like it.