Computer Randomly Shuts Off or Freezes

[Chaosinsanity]

Ok here's the build

ASUStek Crosshair V Formula-Z Mobo

ASUS AMD Radeon HD 7770 2 gigahertz GPU

AMD FX-8150 Zambezi 8 Core 3.6 GHZ CPU

16 GB DDR3 Dual Channel ram PNY Electronics

850 Watt Power Supply not sure what manufacturer

Windows 8.1 Operating System

I use Windows Defender, Malwarebytes, and SUPERAntiSpyware



Anyway the problem is this,

My computer randomly either freezes or shuts down. It has frozen while even on the BIOS. I've used CPUID and HWMonitor to check temperatures. I've checked in the event log to see what happened. All it says is that it shut down. It's a 2 year old build.
Not sure exactly what other information is needed to help identify the problem.

[Geek-9pm]

The usual thing is to suspect the PSU (Power Supply Unit.). Even a very good PSU may be susceptible to sudden shutoff. So using a spare PSU is the normal way to test fort this kind of problem. Otherwise, it is very time-consuming to try and pin point the specific cause.
If the spare PSU does not eliminate the problem:
  Use a different wall plug, even on a different circuit. **
  Remove the DVD and see if the problem clears up.
  Remove the hard and run it with Linux 'Live' CD..
  Replace all RAM sticks with one spare RAM.
  Replace the graphics card.
Of curse, the last thing is the motherboard.
 
** Rare, but faulty electrical system can do this.

[Chaosinsanity]

I wish I had extras but the only extra I do have is a power supply so I'll try that