Mate ur problem is either the compatibility with win2k, or you are asking too much from ur graphics card, what resolution are u playing at? What colour 16-32? Which options do you have enabled.
I have a pentium 4 1.7, with 256meg and a geforce 2 mx400, i thought my comp could handle andything and turned on all the options that made the game look sweet, but the comp couldnt handle it and the framerate was crap. So I went back and made everything defualts and the resolution to 1024-768, 32 bit, and all games run fine and 50-60fps.