Imac G4 14in won't boot

Hi,

Moved in to our new home a couple of months ago.

Sorting through the loft and the junk left, I found in it's box a white IMac G4 14in with charger, nothing else, no disc, software, just the laptop and charger.

It is in superb condition, could I be so fortunate?

Couple of days ago I got to play, charges ok, turns on and off, the screen lights to the Apple logo and that's it, no further boot up sequence.

When I turn on I can hear either the fan or the HDD and one chime, then the screen lights and the apple logo.

Is it worth repairing, what could be wrong, HDD, RAM, Board, what?

If I need a new HDD, where would I get a an Mac OS from.

Is there a video on line I can view to tell me how to take it apart, I'm good with a screwdriver or should I bother?

Completely new to Apple, never owned a lap top.