before you go to extremes...
Your sysmtoms are hardware related...
Rerun the hardware installs from their disks, (sounds like a video card mixup) and let them redo your video drivers. Your system may be runnning a generic driver and setting.
What kind of computer is it? Brand name, store bought , or pieced together?
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The RudeDawg
Known in these Forgotten Realms as Perin LightEyes