Video card problem wont play video full screen?

I have a club geforce 7600 gs video card pci express x16 and when i play video at full screen the video goes wrong after a minute and seems to have 2 video images on screen out of phaze with each other then the screen either goes black or graphics on windows desktop breaks up it does this with any video at full screen avi dvd wmv until i restart windows no videos play, but it will play any video as long as its in a window

my computer is windows xp, athlon64x2 dual core 3600+ 2.01ghz 1 gb ram any help anyone? I have tried all video packs such as k-light and so on|||try your display settings advanced tab then video settings

GL