does the machine actually have an XP licence cert on it?
Whats the exact wording? Just thinking - the Uni may have put a VLK licence on it, but the machine should still have orginally come with an OEM licence sticker, and you should be able to use that with an OEM disk
KeyFinder | Magical Jelly Bean will find your existing XP key.
All you'll need to do is to ensure you have a media CD from which to reinstall.