I have an i7 machine that is acting weird. I boot it up and every thing seems to boot right, then 15 or 20 minutes later I look and it is off. I have ran temp checks on the cpu's, video card and MB and everything is well within specs. then I boot it up and set down and use it and it runs for hours. today I loaded u tube and started videos and let them run for about 5 hours and the machine never shut down. anyone have an idea as to what is going on. Ideas needed.