* Uninstall Windows Vista on a multiboot system
Note: Applies to all editions of Windows Vista.
You cannot uninstall Windows Vista. However, you can change the code that starts the operating system (often called the master boot code), and then remove Windows Vista from your multiboot system and return to Windows XP or Windows 2000. You will need your Windows Vista installation disc for this procedure.
1. Insert the Windows Vista installation disc.
2. Click the Start button , click All Programs, click Accessories, right-click Command Prompt, and then click Run as administrator. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
3. Type [DVD drive letter]:\boot\bootsect.exe /nt52 ALL /force and then press ENTER.
For example, if the DVD drive letter is F, type f:\boot\ bootsect.exe /nt52 ALL /force.
4. Eject the Windows Vista installation disc.
5. Restart your computer.
Your computer will start in the previous version of Windows that you have installed.
6. Delete Windows Vista files and folders, such as the Program Files, Users, and Windows folders, manually.
Till the Step5, you can do:
Format the partition/drive where you had Vista installed.
Remove two files (Boot.BAK & Bootsect.BAK) on your XP root folder (C:)..