2he put a new motherboard in at some point. Will this cause problems?"
A restore will therefor be a waste of time as it will have incorrect drivers for the new board.
i have a Windows XP (SP2) from my own PC, so can i just use this to re-install XP, but put the serial number from the packard bell in instead (or will the fact that this was for a SP1 version of XP mean this wont work?)
should work ok