System specs:
P III (3GHz)- 2GB RAM (DDR2) ATI X1600PRO (512AGP). Nothing special!
I have set 4x antialiasing and 8x ansiotropic filtering as you have pointed me.
Particles to 100/Vsynch enabled
Only some reduced FPS douring the explosions
I always turn off everything from task manager and the internet connection as well