G5 power Mac trouble: Not loading osx

Hi folks looking for a bit of help here, My mates just got himself a g5 mac of ebay and brang it to me to help him get it working.
Im no mac expert just use them at work and have a mac book, but no more than him on the subject so trying to help!

In the product description of the item it said it just needed a start up disk to work, i have no start up disk for it so cant test this right now.

Is this common with macs? im sure my book came working right away with out this trouble?

when i press the power button the led lights up and makes 'the mac on noise'
and apears to be working, the display doesnt do anything and it sits there sounding on but doing nothing.

is it possible that the machine has no os installed?

has my mate been ripped off and paid for a broken mac?

any help would be ideal, as im out of my depth here, ta

Edit: the monitors a Apple Cinema Display.

When you say shifted do you mean come loose? have just had a look and it apears to be firmly in its slot.

The Monitor apears to be powerless, no display at all.

there is a hard drive in there yes and its connected.

Sun Baked said:

I mean shifted, but still firmly in the slot.

Moved just enough to break the signal on a few traces, in the slot.

Apple's first couple repair tips beyond is it plugged in, check the cable/and card socket for bent pins, and resetting PRAM is -- reseat the video card. But there is/was a site on diagnosing video problems on the G5, but I have no idea where anymore.

Click to expand...

Ok will give this a go

Took the card out and put it back in, still no joy