Hard Freezing Randomly

[DiSektion]

Hi, I've been having a problem that has persisted for a while, I am having suspicions but I want to get your opinion/help to confirm them.
Randomly in time periods seemingly of 1-24hrs of being powered on my PC will freeze entirely, Have to Hold power button down to Hard-reset.
Screen will still show whatever image was being shown, No sound, USB Devices all turn off. And no messages in Event Log to show that its related to Software, And this problem has persisted over new RAM, HDD Re-formats, new GPU.

Specs:
Corsair CX600w PSU
ASUS P8B75-V
i5-3570k @ 3.8GHz
AMD R9 390 2GB
8GB DDR3-1866mhz (forcibly downscaled to 1600 because Dodgy BIOS settings not working)
Windows running @ Western Digital 1TB Blue HD (New since 2012)
Last Fresh install of Windows was Nov/2015

I'm starting to suspect its either my Motherboard or my Power Supply but I was hoping to get some input here for help.

 

[cin19]

1) Go into the BIOS to check the +3.3V, +5V, and +12V, if the MB does not have this feature, use the HWiNFO64 http://www.hwinfo.com/download.php but you should update the chipset drvier first, just make sure the sensors have newer driver. chipset driver https://downloadcenter.intel.com/download/20775/Intel-Chipset-Device-Software-INF-Update-Utility- mkae the PSU can handle the r9 390.
2) Check the CPU/GPU by the HWiNFO64, maybe they are overheat.
3) Using the UUD uninstall the AMD gpu even the intel iGPU driver too, then reinstall the AMD driver. * may try the old version too. DDU http://www.guru3d.com/files-details/display-driver-uninstaller-download.html
4) May test the RAM by MemTest86 http://www.memtest86.com/download.htm

 

[DiSektion]

1) Go into the BIOS to check the +3.3V, +5V, and +12V, if the MB does not have this feature, use the HWiNFO64 http://www.hwinfo.com/download.php but you should update the chipset drvier first, just make sure the sensors have newer driver. chipset driver https://downloadcenter.intel.com/download/20775/Intel-Chipset-Device-Software-INF-Update-Utility- mkae the PSU can handle the r9 390.
2) Check the CPU/GPU by the HWiNFO64, maybe they are overheat.
3) Using the UUD uninstall the AMD gpu even the intel iGPU driver too, then reinstall the AMD driver. * may try the old version too. DDU http://www.guru3d.com/files-details/display-driver-uninstaller-download.html
4) May test the RAM by MemTest86 http://www.memtest86.com/download.htm

My VCore is changing between 0.800v to 1.000+ish
+12V is at 12.192V
+5V is at 5.080V
+3.3V is at 3.328V


I ran MemTest86 and there were no errors, also uninstalled my GPU drivers and reinstalled, I also installed the Chipset Drivers. For now I haven't had a crash yet but i'll get back to you if it happens again.
Also I should mention that that crashes always happen when nothing intensive is happening, as when I game and 100% my CPU @48C and GPU @ 72C it doesn't crash or throttle.

It ususally takes awhile for the freeze to happen but it usually happens every 20ish hours.

 

[DiSektion]

Haven't had a crash/freeze since I did all of what you said, thank you.