theres really no way to tell what its from right away.
the firmware upgrade that makadon speaks of seems like your first priority.
then try changing the ram stick, if that doesnt do the trick, try using a different CPU processor, if that doesnt do the trick then you will need to replace the whole motherboard.
i've dealt with many cases involving constant page faults, and it's a hardware issue. windows xp is not cooperating with your hardware.
now there might be hope with software. If you are using windows xp sp1, install windows xp sp2. if sp2 is the current version you have,then change back to sp1. alot of times this works.