How to Uninstall and Remove Windows 7 or Vista Leaving Windows XP on Dual Boot System

Windows operating system supports dual-booting a PC, where users can install multiple OSes and select which system to boot up to on machine startup. If you have installed Windows 7 or Windows Vista on top of current existing Windows XP to make the PC a dual boot system, but now decided to ditch or dump the Windows 7 or Windows Vista
partition to revert to the old good classic Windows XP follow the guide below to uninstall and remove Windows 7 or Windows Vista to leave only Windows XP without having to reinstall the OS, and without affecting saved files and data.

Important: Do not use this tutorial if your dualboot system is Windows 7 and Windows Vista.

1. Boot up and log on to Windows XP desktop.
2. Insert the Windows Vista or Windows 7 DVD installation disc into CD-ROM or DVD-ROM optical drive.

Alternatively, mount the Windows 7 or Windows Vista DVD ISO image on any virtual drive.
3. Run Command Prompt, or click directly to Start menu -> Run command.
4. In the command prompt or the Run text box, issue the following command and hit Enter:

[DVD Drive Letter]:\boot\bootsect.exe /nt52 ALL /force

For example,

If the DVD drive path is D:, then enter the following:

D:\boot\bootsect.exe /nt52 ALL /force

The step will remove the boot menu to select operating system to start.
5. Remove the DVD disc and restart the computer.
6. The computer will boot up with Windows XP installation partition.
7. Manually remove files and folders of Windows Vista or Windows 7, including Windows, Program Files and Users folder. If you’re installing to separate partition, just format the partition to clean it instantly (with FDisk, Disk Manager of Computer Management or third party partition management software such as Partition Magic or EASEUS Partition Manager).
8. On the root system folder of Windows XP, delete Boot.BAK and BootSect.BAK. The two files are remnant backup leftover files of previously installed Windows Vista or Windows 7 bootloader, but no longer useful for Windows XP only system.

Tip: NT52 is the MBR (Master Boot Record) used by Windows XP and Windows Server 2003, while Windows Vista uses NT6. So if you’re uninstall Windows 7 in Vista/7 dual boot system, change the NT52 in the command to NT60.

Fast Shortcut: It’s also possible to format the Windows Vista or Windows 7 partition straight away, and then start the computer with Windows XP Setup CD to repair the system partition, or run the “bootsect /nt52 c:” command above from the \boot\ folder of leftover OS immediately to repair the boot partition.

Tip: When startup repair the boot record after removing an installed operating system from dual-boot or multi-boot system, always use the highest version of Windows installation DVD/CD to perform the repair. For example, in a tri-boot PC with Windows XP, Vista and 7, after uninstalling Windows 7, use Windows Vista to repair the system. If the PC is restored and reverted back to Windows XP, then use the Windows XP setup CD.