Installing and booting to old HDD in new comp.

Not sure if this is the correct forum but here goes. A friend's mobo dies. He goes to buy a new/used PC. He pickes up an athalon XP machine with an MSI mainboard. Old machine is an Athalon XP with ASUS mainboard. In an effort to save reloading all his programs onto the new HDD we took the HD out of the old machine, popped it into the new machine, set the bios to boot to the old HD thinking we would be in business. Not so.

Is there a way to get the mobo drivers onto the old HD or do we just start from scratch with the new machine?

Thank You,

Woody