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. It sounds pretty simple to do (just some registry changes), but you can?t install Service Pack 2, so you might try to slipstream in the changes to your modified install disc (if that?s even possible).

GizModo