I have been having a major problem in the past few months but it has become unbearable to continue with the issue I'm having.
In the range of 30 seconds to 15 minutes of no games or any full screen programs system will freeze and display a grey or different colored screen, mouse will dissapear from screen and wont accept any keyboard strokes (ctrl + alt + del, esc or anything). To make it more difficult this issue can not even happen some days.
The only way to get out of the problem is hard restart, restarting via reset button on my PC does not get system back up only just sits on black screen. Have to switch power off to PSU and back on then can start PC up.
I've run FurMark 1.9 for sometimes 1 minute and the problem will start, freeze and orangeish colored screen. I've run FurMark again straight after rebooting the system and problem wont happen for 15 minutes. I will stop the test and run it again and problem wont happen at all, it seems to be all over the place and i cant determine what the cause is with its erratic nature.
Ran Prime95 with passes on all RAM, CPU and PSU tests.
Tried changing Memory clock down to 1100Mhz and GPU to 800mhz, same problem.
Graphics card also has a safe mode for all stock settings which i have not overclocked card anyway but same problem happens in safe mode.
Currently running 11.6 drivers but have tried 10.9, 10.11, 11.3, 11.4.
Have tried various fixes on searching many different forums which include wiping and reformatting OS, Reinstalling with earlier version drivers, Running with no software installed and missing Win 7 SP1 - Problem still happens.
Have never over clocked card, and problem has not been present for approx 6 months until it came out of no where.
AMD Phenom(tm) II X6 1090T Processor (6 CPUs), ~3.2GHz
6GB memory GSKILL ripjaw
Direct X 11
ATI Radeon HD 5870 2GB (stock edition) - GPU 850mhz, Memory 1200Mhz
OCZ Vertex 60GB SSD as primary drive and 1TB secondary drive WD 64mb
24" 60mhz 1920 x 1080 Samsung screen
Windows 7 64 bit Home premium (SP1)
800W gold pro cooler master PSU
MB: gigabyte GA-890FXA UD5
System is not overclocked whatsoever and is running all stock settings.
Ran Video Memory Stress Test v1.7.116 which gave error "Error at [403E9000]: must be 00FFFFFF, but found 00F0F0F0 (bits: 00000000000011110000111100001111)".
Purchased card on 12/10/10 so can still take it back, but of course thought id see if i can get some help first
NOTE: From looking in windows event viewer all it seems to record is "Display driver has stopped responding and has recovered"
A slowly failing power supply can cause all sorts of strange issues, it doesn't just shut off. I would think an 800w gold PSU would not have a problem but the symptoms sure make it sound that way given that you have tried a fresh windows reinstall and all those drivers, or maybe the card it's just a bad card. You might try installing MSI afterburner and bumping up the vcore voltage and see if it helps at all.
I would try testing the graphics card in another machine first, or exchanging it or having someone test it if it isn't a costly PITA to do so. And try another PCI-E slot on your motherboard and different connectors to the PSU if you havn't yet. I would rule out the graphics card and the motherboard before replacing the PSU given the quality of the one you have.