XP and old MS Windows can be restored by the installation CD or just a Dod bootable floppy with fdisk.exe inside. Task B1 and B2 in the last link of my message refer. Either method works on any Dos and MS Windows as far as I have tried.

The new Windows Vista now has its own MBR and must be restored by Vista's own installation DVD. Task B7 of my last link in the signature refers.

It is fairly standard that an operating system on a PC will have a ready-made mechanism to restore its MBR.