dude. get a gf2 mx 400 pci..
right now on pricewatch, there is a creative labs one with 32 megs of ddr... it is OEM, but for $76 i think that this will greatly improve yuor video.
also, there is better ones, but howmuch are you allowed to spend?
and i will have to agree with everyone else. you will probably be better off buying a new mobo. but it all depends on what case and psu you have i suppose. did your dad buy that thing PRE-made? and if he did...then who made it. compaq, dell, hp, micron. or a computer store.
if you hook us up with some more info, i am sure that someone will be able to hook you up with some suggestions.
-DAvid