I have everything on medium, with the exception of aircraft, maximum settings on those. I usually hover around 20 or 30 fps at low resolution, but I am still doing some tweaking.
A8N-SLI 939
3800 X2 64
nVidia 7800GTX (SLI)
2GB Corsair DDR400 Memory
Western Digital 230 GB HDD
Windows XP SP2