I don't know why you have grub as a bootloader if you only have XP and 2000 on the computer.

To Remove Grub From Your MBR. just use the command fdisk /mbr...
boot your computer with win 98 or ME and start computer with cd rom Support. at the command prompt enter the command fdisk /mbr and then reboot your computer... your Grub is removed...

Try that.