Interestingly I installed 169.28 beta drivers, and lost the ability to turn on shadows, but did get the ability to run the game with maxed out graphics (including v-synch and anti-aliasing turned on) at around 20fps - which is quite playable. Switched back to 169.21, and got the ability to turn shadows on again, but then performance at 12 fps (not so playable). Am glad I have the choice, however.
Running XP dual core with 2gb RAM and NVIDIA 8600 GT graphics card.