Smurfjet,
It would help knowing which Vid Card and monitor you have along with the Drivers you are using.
When you set your desktop, I would recommend using 16Bit Color since there is no reason to render your Desktop in 32Bit Color. (Especially if you are playing a flight sim or other game, you do not want Windows rendering your Desktop in 32Bit Color in the background. Just slows down your comp's performance.) Depending on the Monitor, I would usually set 85Hz for CRTs and 75Hz for LCDs.
Take Care,
Richard