PC won't boot up

[Margret]

My Pc will turn on but will not boot up. It will not start the keyboard, mouse or monitor. It was working fine, I went to answer the phone and when I returned, everything was off, I turned Pc back on, will light up but not anything else. It is a ASUS only two years old. no new software installed, nothing changed about it at all. any ideas?

 

[Cobalt006]

Sound as though maybe your power supply went out.