Computer turning off...tried everything!

just an odd thought,
one of the windows cetified drivers being loaded when not in safe mode is turning the system off.

which one would be problematical, but odds are that this is what is causing it.

Being able to reboot immediately does not rule out overheating. Even the fastest reboot takes long enough that near-boiling temperatures (80+ C) reduce substantially, even to halfway between their full-load temps and the ambient temp inside your case. Try running with the case cover removed. If that prevents your unwanted rebooting, you have been overheating. If that's the problem, add case fans, beginning with one blowing out of the case. Exhaust fans are as important to get hot air out of your case as intake fans are for drawing cool air in. Generally, it's preferrable to have at least as many exhaust fans as intake fans because "nature abhors a vacuum" - when you evacuate the hot air, cool air will flow in through any ventilation holes, not just where you have an intake fan.

Other observations that lead me to suspect that overheating may be the real problem: (1) time of year, and assumption that you live in the Northern Hemisphere, meaning that you started noticing this around the hottest day of the year if you posted soon after noticing the problem; (2) Safe Mode does not mean just a minimal software config, it means that a minimal set of drivers are installed. Your graphics card, for example, is taxed much less to display in 16 colors at 800x640, or whatever the exact specs of Safe Mode display resolution really are. So in Safe Mode one of the main differences you expect is lower demands made on all your devices.

The good job of troubleshooting you have already done really narrows down possibilities.

At this point, I would suspect video card as the problem. Safe mode and standard old VGA does not utilize many of the video card features nor all of its memory.

Symptoms are consistent with faulty video memory.

Swap video cards and see what happens.

Dalton

I agree with Dalton, but first try removing then re-installing you video card driver

It worked with me most of the time

This could be caused by driver, service, or a failing device.

Check Event Viewer (Application and System). Once identified, disable appropriate service or uninstall/reinstall/update driver. Or replace the failing device.

Also make sure Automatically Restart is unchecked in System Failure setting.

i'd go with willcomp, video card sounds brilliant.
what about going after the power saving stuff? turn it off in windows, turn off the power saving 'feature' on the nic, update the bios.
yank all the cards out you can and put em back in one by one. with newest driver...