Guess he means CPU. And yes all normal.

Ive left Windows to boot up and left it on the desktop without opening any software. So far is good. Software couldnt cause this surely?

Only thing i know thats updated is Windows on Weds (PC was fine all Thurs so dont think its that), MSE and Firefox today.

Had my PC on for 24hrs since it started happening and so far been stable.

I did notice that during the time it was randomly turning off, I had a faulty fibre optic xmas tree connected downstairs (same electrical circuit). The tree was drawing too much power, and im wondering if this could have been the cause? Seems odd as it was the only device effected in the house, but I wonder if this was drawing too much power, it was effecting the voltage levels going to the PC?