Random BSOD and failed boot

Hi everybody, I'm a new user from Italy. My name in Enrico.

Since June 2014, when I upgraded my PC to a better one, I'm experiencing random BSOD and also boot failure.

When I change my hardware, I kept only the DRAM (Corsair Venengance LP DDR3 LP), and the rest was changed.

A couple of days after my upgrade I started to experience random BSOD (Cache error or IRQL Less or Equal). After a Month sometimes windows fail some boot, asking me to restore in a previous working state.

In January 2015 I decided to fix this problem: I changed ALL components, except DRAM, Bluray Reader and PSU.

So my actual system is:

Motherboard: SABERTOOTH Z97 MARK 2
CPU: Intel Core I5 4670k
RAM: Vengeance® Low Profile — 16GB Dual Channel DDR3 1600
PSU: Corsair CX600
LG Bluray Reader/Writer

And I'm still having the problem... I also tested the Ram on Memetest without errors, and I'm having BSOD also after a fresh install of Windows. I also tried with a Ram of a friend of mine, but I didn't have any BSOD in two weeks, but only the "windows must be restored" error...

I'm start to think that could be a Ram problem, but honestly this problem it's starting to make me crazy...

Thanks for any help.

Greetings from Italy

Enrico

Random BSOD and failed boot