There are three Methods

• Using MS-DOS/Windows 9x boot disk
  • In order to remove the GRUB bootloader from a Linux and Windows XP machine, boot with a Windows 9x startup disk or CD and execute the MS-DOS command:

    fdisk /mbr
    

• Using Windows XP boot disk
  • Boot computer using Windows XP (Windows 2000) setup disc / CD / DVD. Next, type the following commands:

    # fixmbr
    # exit
    

• Using Linux
  • You can also use dd command from Linux itself (it removes partition table):

    # dd if=/dev/null of=/dev/sdX bs=512 count=1
    

  • Just remove MBR, without the partition table (see comment below):

    # dd if=/dev/null of=/dev/sdX bs=446 count=1
    

Reference

• ​http://www.cyberciti.biz/faq/linux-how-to-uninstall-grub/
• ​http://en.opensuse.org/SDB:Uninstalling_the_Boot_Manager_GRUB_from_the_MBR
• ​http://www.linuxquestions.org/questions/linux-software-2/remove-grub-from-win-xp-19731/
• ​http://indeepnight.blogspot.com/2007/08/fixmbr.html