I just built a new machine myself. I am also running XP and can only highly recommend AMD, but if Roger says no, then no!
I also agree with Hashts. If you are not going to overclock the machine then just about any name brand RAM will be fine. PC3200 will be fine and if he is going to play WoW (I'm still single because I'm addicted to it) then I would recommend trying to get 2 gigs of ram. It makes a very big difference when changing zones and entering instances. I still have trouble with Iron Forge (he'll know what I'm talking about), but I don't fall down into things anymore.
-j
