Well players, after having ALL of the above symptoms in World at War, I think I have solved it. I used to get random hard shutdowns between 5 and 30 mins....I tried the below and guess what..NO shutdows.....
Go To ->
System and Security
Under the Active Tasks panel, I had a task named "RacTask" scheduled to run 1 hour after the power on.
I noticed when the time to start that task comes, my computer reboot...
So I disabled that task, and my computer don't reboot anymore now.
Seems a joke that the RAC service who is the responsible to check the reliability of the system, was the cause of the reboot
Hope this helps as this was driving me crazy.....