Benchpresser, I need some more information on your issue please.
First, what video card are you using? and have you tried updating the graphics drivers?
Second, what amount of virtual memory are you using? and is windows controlling it? (it may need set to a static number to give you a performance boost).
also look at your graphics options in game
any other applications running outside of the game?
have you tried playing it in full screen window?