It might matter. It might be looking for a certain BIOS (on my Dell, it's called SLIC 2.x) and if it doesn't see an 'HP' BIOS, it may detect it as a virus and stop installation. And no, even if you restore you can't downgrade. You need to find an original XP 2002 SP2 disc (to match your key) and install from that. Maybe download one from a torrent site or have a friend that might have one? You can even try smaller mom and pop type computer stores, see if they can burn you a copy for a nominal fee.