I built myself a new computer. Everything seems to be working fine, but it will sometimes freeze at random times or just crash. Now when it freezes, it just stops. I have to hold down the power button to get it to turn off and then reboot it again. Sometimes, the computer will just restart itself. This can be at anytime, too. It happened once when during Windows Automatic Updates, and it happened another time when I was extracting a file. What do you guys suggest I do to fix this?