update your Graphics drivers, if you dont know what graphics card you have, google 'GPU-Z' download and install/run it, and you will find out what graphics card you have, then either go to the Nvidia or ATI site and download the drivers.
you never have to uninstall a game with steam if you think it's damaged, right click on it in the games list, go to proporties, local files tab, and then Veryfy integrity of game cache.
make sure that you dont have any of the following running:
a backup tool
a virus/spyware scanner
a defrag tool
a registry repair tool
or anything that will need to use the hard drive.
although it probably isnt a problem with something running, it's probably that your graphics card cant cope with the game.
updateing the graphics drives is the only thing you can do, as tehre were huge performance increases with driver updates that came after the game, and are still comeing out.