Change Volume Licensing Product Key on Windows XP SP1 "Because of changes in Windows XP Service Pack 1, Windows XP-based computers that use a leaked product key that is known to be available to the general public may not be able to install SP1 or automatically obtain updates from the Windows Update Web site." To change your product key, follow these instructions.

Would you like to retrieve your XP Product Key?
RockXP is a free program that will allow you to retrieve the XP product key that was used when you installed Windows XP. You'll need a tool like this if you misplace your serial sticker.