card, computer, software. any updates for anything you have.
like .net (
http://www.microsoft.com/NET/Download.aspx )
also look here for the newest drivers )http://www.nvidia.com/Download/index.aspx?lang=en-us )
do you have vista or xp.. get the service packs for whatever one you have..
and also try to turn down the settings of the game like shadows and water detail.