Spycoo16 Are you playing in fullscreen or windowed mode when this happens, and does switching make the game look right again? Is this after you've restarted your computer, or have you been letting it run for a while, and maybe had other applications running in the background? If you have a laptop, is it plugged in or running on battery?
For reference, please also provide a dxdiag. Click Windows key-R, enter dxdiag in the run box, wait for the scan to finish, click "Save all information," and save the file to your desktop. From there, you can attach it to a reply using the paper clip (Attachment) icon included with the other formatting buttons.