Last time I post about system hangs.

[FoxiStatis]

I'm thinking of trying OCCT - 3.1.0 Download - EXTREME Overclocking

 

[Tenenbaum]

I'm thinking of trying OCCT - 3.1.0 Download - EXTREME Overclocking

If it were likely your CPU that was unstable, you'd probably be experiencing random shut downs, rather than random hangs.

Are you sure your brother won't let you borrow his, just for diagnostic purposes?
Try asking him!