STOP!
If you simply follow the instructions below you will lose everything on your PC so read and perform the steps outlined on the reinstall windows homepage first to ensure you have taken a backup of all your files!
The following guide applies to both 32-bit and 54-bit versions of Windows Vista. What’s the difference? The number of ‘bit’s basically refers to how many things can be done at the same time, the higher the bits, the more multitasking can be done. (Think of it like a man having a 32 bit brain and a woman having a 64 bit 
) If you want to use the 64-bit version of Windows Vista you have to have a 64-bit processor, you can’t just run it on a normal PC. If you have a 64 bit processor it will say so on the front of the case or you will know about it because you specifically speccified it when you ordered your PC, otherwise assume you have a normal 32-bit processor.
So now that you have backed up everything on your PC you can reinstall Windows Vista. With your Windows disk in the CD ROM drive restart your PC and look for the option on the very fist screen to enter Startup options, which is usually either the delete key or the F12 key. Sometimes you have to literally jump on this key the moment the first screen appears, you can even hold the key down as you turn the machine on to ensure it gets read.
This next section is the same as the instructions for other Windows versions it is not specific to the operating system and is part of the physical hardware device that makes up your PC. So now you should see a blue menu screen known as the BIOS screen. Whilst all are quiet similar they are not all the same so what you are looking for is the Startup Options menu, wher you will see that the C Drive or hard drive 0 is set to the be the first device. This means that on startup the computer will look on the first device for the system files to load, so by changing this from the hard drive to the CD ROM we can bypass the usual windows startup and launch the Windows installation process.
To change the order of the first device follow the instructions which normally involves using the Page Up/Page Down keys to change the order of the list. Once you have set the CD ROM to the initial boot device press the F10 key to Save and Exit, or other key as diercted on screen if it is not F10 on your system. This will require you to confirm your action and your computer will restart. Sometimes upon restarting you have to press any key to confirm that you do actually want to boot from the CD ROM during the boot up sequence. This will start the Windows installation process by copying the installation files.
When the installation files have finished copying to your PC you will be presented with the Install Windows screen, follow the instructions as directed and click the Install Now button and carefully enter in your own personal information when prompted.
On the page titled Get important updates for installation page, Microsft state that they recommend getting the latest updates to help ensure a successful installation and to help protect your computer against security threats. However, as you will need an open Internet connection to get the updated installation files and the disc has worked successfully many thousands of times, you can leave this stage until later if it is more convenient.
On the next page you will be asked to type in your product key and although this is optional at this time it is recommended that you do this right now and do not continue if you do not have the key to hand as you will be tempted to run the pc in demo mode and in 90 days time you’ll have a proble,. So if yo udon’t have the product key, go and get it, or just enter it in off the side of the case. If you have no Windows Vista license sticker then your PC might not have been designed for Windows Vista or it’s source might be questionable.
On the next page read the license terms and if you accept the license terms, click I accept the license terms.
Follow the instructions on each page as they appear. On the page titled: Which type of installation do you want? click Custom.
On the page titled: Where do you want to install Windows?, select the partition where you want to install Windows.
Click Next to begin the installation (you might see a compatibility report but as you are reinstalling Windows Vista you can ignore that.
Next follow the instructions on screen to complete the process.
If the above all sounds too complicated and you are looking for the easy way to do it
(without buying a new PC) then click here now!
Next see the page: Reinstall Windows Drivers