pc shuts off by it self

[Bigbrit]

Have had several Power Supplies recently that suffer from "Blown Capacitors" usually found on motherboards.

They run for a little while and then shut down with no warning, they can also do other strange things while Windows is running.

Replaced it with a good make and the problems went away.

If you have a really good friend, ask him/her if you can "borrow" their unit and test it.