Computer crashes, forces me to do a cold restart.

[Moridn]

ATI Phenom 2.8 Ghz Hex-Core.
AMD Radeon HD 6870.
Win 7 64-bit.
8GB RAM.
MSI 890FXA-GD65
Roswell RV700 power supply.

Please help me yall. I have never seen something like this. During use, after about 2-3 hours after power up the box will suddenly, with no warning, no error code, no noises, will cut off. The monitor will turn black, and you are forced to use the power supple toggle on the back of the machine to cut the power as the manual power and reset switch on the front of the machine will not work in this case. I have updated all my drivers thinking it might be a display driver problem, and have reinstalled windows. Can anyone give me any kind of clue on what this could be?

 

[DriftingJoint]

ATI Phenom 2.8 Ghz Hex-Core.
AMD Radeon HD 6870.
Win 7 64-bit.
8GB RAM.
MSI 890FXA-GD65
Roswell RV700 power supply.

Please help me yall. I have never seen something like this. During use, after about 2-3 hours after power up the box will suddenly, with no warning, no error code, no noises, will cut off. The monitor will turn black, and you are forced to use the power supple toggle on the back of the machine to cut the power as the manual power and reset switch on the front of the machine will not work in this case. I have updated all my drivers thinking it might be a display driver problem, and have reinstalled windows. Can anyone give me any kind of clue on what this could be?

Is it just the monitor that is turning off or the system turning off?

 

[Moridn]

Is it just the monitor that is turning off or the system turning off?

No, its the entire system. Using intense games does not make it happen faster, its almost completely random.

 

[DriftingJoint]

Does it only happen when you're in a windows enviroment? Try running memtest for a few hours and see if it turns off when not booted to windows. Also you could try running the system out of the case on a non conductive surface for a few hours to see if it doesn't crash. Usually a system just shutting down with no error messages is one of four things, the easiest to test for are the above 2 but;

Faulty RAM or not running at correct timings/voltages
Overheating
Power not being regulated properly somewhere
A short causing your computer to turn off.

So with that being said, if you have a multimeter or another power supply, you can try testing the power supply or running the system with another power supply. Or alternatively you could run another system with your power supply if you have one and not a multimeter. Try with just 1 stick of ram, leave your computer running for as long as it can to see if it crashes, memtest for 7 passes per stick then 1 pass with all sticks installed. Also run speedfan to monitor your temps. If all else fails, I'd say you have a short. What case do you use?