I recently did a full cleaning of my desktop before installing a new graphics card: Radeon 6870. I was coming from a Nvidia 88000 GT. After installing I noticed at random times the screen would go completely grey with darker grey horizontal lines. I thought maybe the drivers were an issue so I cleaned them out and even went as far as reinstalled a clean version of Windows 7. The problem still persists. I wanted to check if the card I bought is faulty or if it could be something else. Prior to this, everything worked fine.