So yesterday I decided to overclock my MSI HD 7870 just to see what kind of performance gains I could get. I opened Afterburner and set the memory clock to max (1450 MHz) and bumped the core clock up by 50 MHz (1100 MHz). Then I ran 3DMark 11 and 3DMark Vantage. Both ran perfectly with some improvement. I then opened Afterburner again and bumped the core clock up to 1200 MHz and increased the power limit by 10%. I then ran 3DMark Vantage again. Again it ran perfectly with even greater improvement but the fans were making a hell of a noise and the card was a bit too hot for my liking (80 degrees Celsius, not too high but I want the card to last). I then decreased the power limit to +0% (leaving the core clock untouched) and 3DMark Vantage. Again ran flawless with similar results. Then I exited and ran SiSoftware Sandra. Unfortunately, I then had to leave so I left it running. When I came back I found a heavily pixelated screen on which I am unable to see a thing. I hit ctrl+alt+delete and immediately blue screen of Windows 7 perfectly rendered. I clicked on Task manager and was greeted with a pixelated screen. I then held in the power button to switch the computer off. Then I switched it back on again and set the card back to default values. I've run a couple of benchmarks and the card appears to be performing as it always has. Can anybody explain what happened here?