Sounds like something in your system is set wrong to me.
My XP1800 maintains 30+ fps at 1024x768 with medium detail settings, cars only in mirrors, and 2x Antialiasing and 4x Anisotropic filtering.
You do have a minor hit against you in running PC2100 (266mhz DDR) ram, but since your FSB runs at 266 also, the difference of pc2700 shouldn't be too significant.
Also, your GF3 Ti-200 is a pretty slow card relative to what is available these days... it's roughly equivelent to a Radeon 8500 in terms of most benchmarks, which is to say that a FX5700 Ultra or Radeon 9600xt would be much faster when playing most games... GP4 however is highly processor dependant, which is why your performance seems strange.
I'd love to see how your system is configured in terms of bios settings, etc, and also run something like Hijackthis to see if you have a lot of unnecessary or unfriendly services (read: trackers, autoupdaters, download apps, etc) eating up resources.
If you use MSN messenger, please add me to your list (above email address) and shoot me a message. I'll be glad to walk you through some things which may help to determine the problem.
Post Edited (03-03-04 02:20)