Well, it could just be a loose, or bad, cable if it's a picture taken with a digital camera. That wouldn't show up on a screenshot though. Otherwise I'd say currupted drivers or hardware malfunction.
ouch .. looks like bad hardware. did you install new drivers recently or have you changed your gpu recently? overclocking -> overheating? inadequate powersupply?
Try using Prt Scr and going into MSPaint and then go to the Edit tab and select paste then go to file save as desktop.jpg so we can get a better idea of whats wrong.
