I *think* all you have to do is reactivate windows. I stuck a hard driver from one PC into another for testing the other day, and got a msg from XP saying "there has been a significant hardware change, you must re-activate Windows within 3 days"......
Don't know what would have happened if I had re-activated XP, maybe it would have allowed it, or maybe I'd have had to call customer support?
Cheers
EA