Apparently my new computer had more than one problem.
I've solved the cpu temperaturee problem installing a water cooling system (now the maximum temperature reached is 47, while playing a game 41 degrees).
However my computer continues turning off. That happens when Windows is loading (with both Windows XP and Windows 7, even if more frequently with XP), and sometimes while i'm playing/recording videos/copying very big files.
I noticed that if my computer stays off for 1 entire day, in the next day it doesn't shut down as frequently as it does if i turn it on everyday.
Before you start with your hypothesis, i tell you what shurely ISN'T the problem:
Energy (already checked)
Windows installation (i can't remember how much times i reinstalled both XP and 7)
CPU temperature (as i told before, that is solved)
Theese are my ideas, tell me what are the most belivable:
-One of the 2 rams is physically damged, so when pc goes writing in a damged section it shuts down (is this possible?)
-Hard disk is physically damged (but i should be very unlucky in order to have both the hard disks damged)
-Motherboard temperature too high (i thought about that, but while i do heavy thing i Always keep an eye on mb temperature, and it reaches no more than 30 degrees... is possible that in one second it jumps from 30 to 80?)
-Hard disk temperature (if this may cause computer to shut down, but i don't think so)...
-I'm very, very, very unlucky (it is probable... how to solve that?)