iMac won't boot - diagnostic help please

My mid-2007 24" iMac won't boot.

I hit the power button to start it up, and hear the fan start, but no hard drive noise, no chime, nothing on the screen.

I have tried all resets that i find on google (unplug, wait 15 seconds ect.. holding down keys). Nothing seems to work.

I just had it into the apple store, where my genius ran through basically all of the same steps.

He offered to take it in for a free diagnosis, but as soon as he took down the serial number, he said that he couldn't help. He called my baby 'vintage' and said they they don't diagnose or repair anything 'vintage'.

It's like he just called my wife fat. I'm furious!!

ANYWAY,

I'm pretty sure i've read that there are diagnostic lights on the logic board. Is there anyway for me to figure this out on my own?

I'm assuming that if it was the hard drive that died, i would at least get a grey screen. So i'm thinking power supply?

Any suggestions are appreciated