if you said to a mechanic "my car is making a noise, please give me an exact solution" he would probably want a bit more information. you wont get an exact answer, there are many different causes for your system to shutdown. for us to help you you must list your full system specs, cpu, motherboard, psu (make and model), ram. You must also monitor your temperatures with HWmonitor which is free to download, because one possible cause of the system shutting down is overheating. You need to give us more info, is it completely instantly powering off? does windows just shut down and then power off?