When gaming screen will draw lines, have to minimize to desktop and back to clea

[RonSoda]

This has been a problem for sometime for me. Not sure how else to describe it but when i start a game on my PC it will start fine for a few seconds then the picture turns to hundreds of lines. I then Alt+Tab to desktop and back to the game and it clears it till i finish a mission and the process will repeat itself. Also I'd like to mention this happens to all games.

 

[RonSoda]

Nvidia - It's older an EVGA 7900 GT KO

 

[RonSoda]

I do have 2 video card's so i will pull them out and try each one and see if there is a difference.