Forgot to add- ran 1 pass of memtest and also win7 memtest and got no errors.
These things happen under both video cards so it's not the video.
It's not the HDD because that one got replaced.
That leaves the motherboard and CPU if it's hardware or even memory (i don't trust those tests)
Most frequent blue screens are memory management and pool header
Also - i can't remove memory sticks because i don't want to lose my warranty. I have a Lenovo one and a store one and i don't know about the store policy on this .