check the power cable is plugged in securely at both ends.
is the pc in a hot place like near a radiator ? could be overheating.
The cpu fan may be failing and causing the cpu to over heat, generally the system would freeze first
the power supply in the pc may have a problem
some idi*t my be switching it off when you are not looking, a slap should fix that !! if the pc is dusty inside try giving it a vacum, switch it off first. . .good luck
Dal
June 2007