The computer starts up and runs for less than a minute before shutting down or locking up. This is
a symptom of:

A.
overheating.

B.
incompatible RAM.

C.
a faulty hard drive.

D.
a bad internal USB hub.

Explanation:
http://lifehacker.com/5570909/how-to-prevent-your-computer-from-overheating-andwhy-its-important