You can also help performance by lowering quality of sound in the sound option in the game,and type (dxdiag)in run of your start up menu.go to sound tab in direct x and lower it there also it helped me alot. My system is old compared to a lot of guys,but i get good frames with 4xs antialiasing on.No jaggies 8). I have a compaq with win ME 1.2 duron g4 ti 4200 512 sd ram pc133 no sound card Oh make sure you get the latest sound drivers for whatever o.s. you have(for those without a sound card).
Good advice, but unfortunately, this has been said about 50 or so times already. You're a bit too late :)
Sorry im new,havent seen a lot of the posts yet.
I know you're new, but there's a Search button up top and it helps (and saves ALOT of typing and space) that way you don't post redudant threads :D