changingMotherBoard.........

The wpa file doesn't just store activted state for windows, it tracks hardware configuration when you installed XP, and the hardware configuration at the current time, and if you change your hardare too many times it will require you to reactivate Windows XP. The WPA isnt restored in system restore, so if you want to make any changes back it up, and you can revert to any hardware state and not deal with reactivating.