My imac won't start (flatpanel g4)

My imac G4 flatpanel won't turn on. No sounds. Something similar happened the last time I moved it into another room to watch a movie with it....I bought another just like it, and then it started working again.

It had 'screens of death' issues but those haven't cropped up for ages. It's had ongoing intermittent usb issues. I set the pram about 3 weeks ago and that worked for about 2 weeks.

I pressed the pmu button on the bottom. Nothing happened. I tried starting with control, command, power.

I realize it could be the power supply but before I started cannabilizing my other flat panel I thought I should ask if I missed something.

I had planned to see if I could keep the best of both computers but I don't want to rush it. I need my files and to remove the public library dvd from the drive. (The other computer is more stable but has the older, non-dvd drive.)

Thanks for any help!