Dang bud, wish I had something helpful to say........Uh, I don't think your vid card is fried if windows works OK, but maybe your at the limit of that card, as far as the game is concerned? I really don't know, as I have issues playing the game smoothly myself at the moment.
I have slowly gotten better performance, but still need some adjustments. Alas, the detailed terrain is not for me. Funny how the...undetailed?, terrain reminds me of AHI.
Anyway man, good luck, I'll bet somebody who knows what they are doing will answer and get you up and running quick.
Jenksie