Alienware Desktop not turning on

My Alienware desktop from 3.5 yrs ago just tried to turn it on for the first time and nothing happens, but there a little button on the back on the power supply  when pressed it starts up the fans and lights, but that is it.It's out of warranty so Tech support won't help me. I went over seas just before it arrived so nvr had a chance to use it until now =/ I don't see an off/on switch on the power supply  so i'm guess its either hardware or the pc alien on switch on the front (not sure how to check these ) and probably worth buying a new pc now