It might be worth checking to see if your computer is using your onboard graphics chipset instead of your graphics card?? onboard graphic capabilities are very inferior to graphics cards (of a decent standard).
The motherboard RAM is 512MB and I have a P4 pentium processor 2.53GHz.
In the Display Properties on the Settings tab, there are two boxes 1 and 2 respectively. I clicked on the 2 box which is partially shaded, and altered till both boxes are equal in size. For a time it solved the problem. Though I did that before it was ok for a time.
I have an ati radeon 9000 1 is enabled and 2 is disabled. Do you have two plug in and play monitors? If you only have one i think this should be dissabled.Not sure if this would be your problem though could be yor driver?