Leeeeeeeet's see...
Processor: AMD Athlon 2400+ or better
Motherboard: Any decent mobo that supports said processor should be fine... my personal suggestion would be of the ASUS brand
RAM: At least 512Mb of PC2700 DDR RAM [I think it's PC2700 that runs equal with the 2400+... too lazy to look it up]
Video: ATI Radeon 9500 or better... if you want Nvidia, I don't really have a suggestion here, I don't much care for them anymore...
All this will run quite a bit, so for a quick fix you could [and should] get more RAM that is compatible with your board and a better video card.
My two cents.
EDIT: Oh, and I would have to say it would run better on Win XP, but I haven't run on both to compare.