You should install a new copy of Windows. You will have to backup everything and erase the whole hard drive. I tried this once and Windows didn't even boot. I know I had a copy of Windows 98 on a hard drive once that I put on at least 5 different systems in it's life before I reformatted it, but Windows XP doesn't seem to work that way unfortunately. I'd rather just get a fresh install than have to mess with the restore trying to get it to work with a different system. It's really not that hard to do. Just remember to backup your files onto another hard drive, CD(s), or DVD(s) and you will be ok. It only takes like 2 hours at most to reinstall Windows, and then another little while to reinstall all your programs, but it's worth it.