There is a known bug I believe with the graphic settings. Basically you can turn all of them up all the way, except one: I think it's "Special Effects." ... something effects anyways. That one you have to turn down a notch.
There have been so many threads of this, people need to search before posting :/
But yeah turn down the graphics a notch, and prepare for some kind of registry error when you try to load the game sometime soon as thats also common. the problem tends to happen with ati cards a little more then nvidia cards with this game.