Star Wars: Knights of the Old Republic I & II would probably work (though they would no doubt be jerky in some places). My old PC ran them acceptably and I don't think its graphics card was even as good as yours. (I think it had a GeForce2 MX 400, but Dell built it and I never really got curious enough to see for sure, so who knows.)
zaba_3,if you are really into RTS's (and I mean, you really love them), I very strongly recommend Starcraft and its expansion set, Brood War. They are both incredible RTSes and they have insanely low system requirements too (and they both run perfect under XP).
Also, if you are into FPSes, Soldier of Fortune is a pretty cool (if not exceedingly violent) game which should run fine on your card (not 100% sure about the sequel).
Deus Ex, one of the greatest games ever made. Also check this HTDP project out.
The first stage is boring because of the insane largeness of the map and the new gameplay system and makes people quit from playing, but the rest is brillant, that's the cause which makes this game score 10 out of 10 and so few people know it, I'm sure you'll like it