How do you check your fps in this game?
I have a really bad PC, well it was good when i bought it in 2000 or 99.
Nividia Geforce2 mx 32mb
Pentium 4 around 1.2 GHZ
256mb RD-RAM
60gb HD
WinXP pro sp2
I run the game at 1024x768 with everything on its highest except I don't have lighting effects (my card doesn't support it

). And my game runs smoothly, so you shouldn't have a problem.
One thing I would try is to turn off the sound, in other games if I ran a high sound quality it really slowed down the game. This probably isn't the case but could help. In Msconfig i think you just uncheck certain programs in the services and startup tabs. Another thing you could do is to increase your virtual memory. Also if nothing works and you don't want to tune down the setting try powerstrip:
http://entechtaiwan.net/util/ps.shtm
*Edit* Just noticed you can only get a demo for powerstrip so try Rivatuner
http://www.guru3d.com/rivatuner/ . They have forums there to help you.
Adjusting the settings in there can make a huge differce, but don't overclock too much because you want to keep your card.