If you buy a proper XP upgrade disc, and license, most drivers will install as part of the process. You will have to check Asus' site for drivers specific to XP. That's an old board, I don't know if they have updated drivers... Yes, they do. Last updated in 2002. Go here:
http://www.service.asus.com/#!downloads/c1wax , type in the mobo model, select XP, and go crazy.
A few suggestions. Make a backup of your system to an external drive first, one that can be restored and run if the process fails. Everyone here recommends fresh installs rather that updating an old OS installation; this can be done with the XP upgrade disc and the Win2000 full disc. And, if that's your main machine, get a new one already!