I bought a Radeon 4850HD not long ago, and was using it fine, enjoying its performance over my old 8500gt. However, it often crashed, and the catalyst control centre brought up an error message saying that it had stopped responding, and it had to restart the card, which it did and I could carry on. When this was happening, a red LED would flash on the graphics card for about a second. However, after this happened another time, I turned my machine off to go to work, after it had restarted the graphics card and said it was fine; When I came back, the machine wouldn't start with the graphics card inserted! When trying to start the machine, the CPU fan on the motherboard spins perhaps, 5-10mm, then stops. I have now been using my 8500gt for a couple of months and now I've got a bit more time I'd really like to find out if my PSU went, or my GPU, so i can said it in for repairs!