emerald dude read his specs, hes got an Athlon XP...
and no the 6600GT comes in PCI-E AND AGP.
I'm not too sure of many XP mobos, my motherboard knowledge only really covers Intel. the current mobo u have is agp 4x or 8x ??? it doesnt really matter, ive seen a benchmark between a 6600gt on an 8x mobo and a 4x mobo, not much difference. If ur going to upgrade, just upgrade the graphics card.. if u want to get a new mobo, it will most likey cause more n more issues making u need to get new ram as well, and mite be compatibility issues, so just for now, id upgrade the gpu, and later on whenu have saved a bit more, upgrade the rest.
Sig reinstated. SigSanta