NoOneImportant

I've got pretty much the same system specs (AMD X2 3800+, 7800 GT) and was experiencing the same crappy performance problem. Furthermore, applying the latest 81.98 nvidia driver actually made the problem worse as the main menu would just load up to a black screen (although I could still see the cursor and hear the noises when dragging the cursor over menu options). However, I've found a workaround that lets me play the game without having to revert back to the old 77.77 driver. This does involve poking around in the registry so try this at your own risk. Follow these steps that are found on page 15 of the release notes of the 81.98 driver (except for step 3 which I'll explain below):