I just bought a XFX GeForce 7900GS. It installed ok with minimal problems but sometimes in games I get the garbled screen. Some games it works fine others its garbled. Check out attached photos. Is this a problem with drivers or something else. Please help...thank you

PS I know the pictures are of my desktop but this continues to happen in certain games.

Remove and reseat the card making sure it's fully seated at both ends, and make sure the molex-to-PCIe power cord is connected to the card and the fan is running.
If those are ok, then uninstall and reinstall the drivers. If no luck, then try the drivers at the Nvidia site. If still no good, then check the game manuf's sites for patches.

Also:
-Are you saying that the pictures are of your Desktop when not playing a game?
-What are your system's specs, incl. the power supply?