Turning off the computer in some games.

Hello, I have a problem and can't understand from what it comes, MB someone of you have encountered and can help.

For a start it is worth saying that this problem occurs only in games, and not all(seen so far in Heroes of the storm, Divinity original sin 2, Destiny 2, overwatch). Also the problem does not depend on time spent in the game, i.e. the computer could fall in the first five minutes and a few hours.

Symptoms:
1) the monitor Screen goes out, but no reports of loss of signal(like when you turn off the computer)
2) Sometimes freezes the sound(i.e. from the speakers is heard crackling)
3) Coolers on vidyuhi off.
4) After reboot you may not see the hard drive(BIOS does not see it and change connector helps not always) also very long hanging saver motherboard
5) In the log hangs Windows error Kernel-Power(41)

Check the screw in Victoria showed nothing(Later I tried to put the other screw, but the problem remained), and if the stress tests everything is working stable. Formatting the entire disk and switching the OS to anything did not lead. Firewood new. There is no overheating.

OS: windows 7 ultimate x64
CPU: Intel(R) Core(TM) i5-4430 CPU @ 3.00 GHz (4 CPUs), ~3.0 GHz
RAM: 8Gb
Hard drive: Seagate Barracuda [ST1000DM003] SATA-III
Video card: AMD Radeon (TM) R9 200 Series
Motherboard: Gigabyte GA-B85-HD3
PSU: Chieftec aps-600sb

Actually a question: what can be this?