in the launcher, go to settings, and turn PhysX off. i know that helped out big time with the demo. should do the same for the retail version. as far as
drivers, nVidia has them for 7, so using vista drivers isnt necessary, nor is it recommended.
- also being a graphically intensive game, your card is going to have trouble in any case. my 8500GT had 'hiccups' on the game as well... ( both are budget cards. i would expect great performance to begin with)
-hope it helps.