I have a PC with I7 Processor, 4GB RAM, GTX480, 700 WATT Power Supply.
1) The computer after some hours shuts down by it self. Not normal shutdown. It just turns off. After this failure it opens again by itself.
2) After hours if PC has not yet turn off unexcpectedly. I experience "lagging" in every game i play. The problem is solved when i restart my computer.
Things i did:
1) I've changed Power Supply.
2) I cleaned the PC Tower.
Note: The quality of my Speakers is very bad. I report this because with these bad quality speakers i hear electricity sounds. For example when i play a game sometimes i hear a "zzzzzzzzzzzz" from the speakers. Seconds before my PC turn off i hear a more intense "zzzzzzzzzz" from the speakers. So i always know that the PC is going to turn off 3-4 seconds before it happens.
Note 2: I fear that is a CPU or Motherboard problem. And if it is, i will throw it from the window.. The machine is less than 1 year old and expensive enough...