Please help me with the display settings!

Hi, i got this game today, installed it etc, ran it, ran fine, exept that I cant manage to change the display settings, i goto:

Settings --> Display

and the little "Drag Bars" dont drag, they just stay still, and when i use my scroll wheel to move them, they move but the text doesnt change form "Low" to "High" or whatever, and it just resets itself after i save and exit settings...

I have the settings on "Custom" so thats not the problem, and when i try just setting it to "Ultra High" it dont do anything

I dont think its my graphics card or my specs because they are quite high (XP Home and Nvidia GeForce6800, 512mb RAM and more than enough disk space)

(I have also tried completely uninstalling and reinstalling the game and it does not help, and have tried updating graphics card drivers)

please help.

Thanks