This machine has to run LFS smoothly, even with full grid of AI.
I have Athlon 64 3000+@ 2.4GHz, 1GB of RAM and a 6800GT. All settings turned on from ingame options, 1280x1024 resolution and 8xAA 16xAF, have no problem running it. Full grid ai 30-40FPS for sure.
Well and ofcourse, a 2 year old windows - that's not good no matter how you try to keep it. That might lower the fps in LFS, but not definately, since 3dmark05 score seems to be okay.