Note: Why isn't there a Sub Category for other? My system doesn't fit into any of these manufacturers and it won't let me choose "none."
Hello, recently I upgraded an HD 6850 graphic card to an HD 7870 (Sapphire OC edition), since then the computer will lock up. When this happens, it loses display to the monitor (the monitor just reads no signal.) In addition to this, the fans seem to run at maximum speed, much faster than I've ever heard them run while gaming or performing general tasks. The computer will also not switch off by pressing the power button, nor does the restart button work. The only way I've found to switch it off, is by holding in the power button. So far this has happened three times since the graphic card switch.
The problem with researching this is that it's an awkward case, there's no error message at all to "google" and it doesn't completely switch itself off either. It appears to switch the display off, while remaining powered on. The lights are on, the processor is running and the fans run at maximum. Twice this has been accompanied by a noise, which was a typical continuous really deep beep.
Each time it's happened, has been while gaming. Twice while playing XCOM Enemy Unknown and once while playing Dark Souls. My computer is left on almost constantly, yet it never happens while I'm away from it. It's usually left on over night as well, with no problems. It appears to only be while gaming for extended periods of time.
I downloaded speedfan to check the temperatures, under normal conditions they look like this: