HOWTO Change Windows XP Home to Windows XP Pro
 

We can’t vouch for this hack, because we are too lazy to try it (and we never, ever violate copyrights or EULAs), but kind reader Martin explains the process for turning an Windows XP Home install disc to a Windows XP Pro disc after the jump.

http://www.gizmodo.com/gadgets/softw...pro-105486.php