The problem with testing CPU's is that these testing programs put a lot of stress on the CPU, running them at (or close to) maximum, over a long duration.
Therefore normally they are not recommended

The testing program for GPU's start by testing colors; lines; brightness; sharpness; 3D and then begin to run hard tests on the memory and fan and generally make them run hot.
Usually all these tests can be done just by running a good 3D game.

The issue in regards to your Ram faulting after BSOD (only) sounds as though heat may be a contributing factor.

The Rtenicxp.sys (RealTek Network Interface Card driver) BSOD usually means the driver requires re-install (ideally updated)

Taking it into the place you bought it means I'll wait for the outcome !

Ended up being a bad CPU. Have been running now for 3 weeks no problems.
Thanks all for your help and advice.

Thanks for the update