PC erratically freezes.

[Novokuv]

My PC randomly freezes. It freezes and I have to restart every time. I don't know the cause of this but I do know its not my GPU. I bought my new GPU recently and my PC kept freezing when I had my old GPU.

AMD FX-6350
XFX HD 7970 DD Edition 3 GB
Asus M5A97 LE R2.0
Corsair Vengeance 8 GB (2x4GB) DDR3 1866 memory
Western digital caviar blue 1TB 7200RPM Harddrive
Corsair CX500W

 

[Novokuv]

I changed my ram into different slots. How do i do ram test and hard drive test? Also Im doing virus check now.

 

[Novokuv]

I done Virus scan but I don't know how to run memtest86. I checked many guides but I have no clue what it does. Can someone write a step by step guide? I boot with USB.