Sudden problems with G4 iMac...

Hi, this is my first forum post on here!

I purchased a stunning 17" 1.25GHz G4 iMac a few days ago that is unfortunately and suddenly refusing to boot past the loading bar just before the desktop shows up :/.

I just get stuck with a movable cursor and a blue screen and although the media buttons still work (volume buttons turn the speakers up or down, disc drive ejects etc. with the graphic for each), the desktop will never load (I waited for a while just to make sure)

It will also not boot from disc, CD or DVD, they don't show up in the boot menu after holding OPTION on boot either despite spinning up and seeming to be at least attempted to be read, it gives up after a while.

I have also tried to delete the .applesetupdone file from single-user mode as per many answers I saw both on here and from other sites to see if there was an issue with the user accounts, as well as reset the PRAM and attempting to boot anything from from open firmware (I just get the circle with a line through it doing that).

I'm really at a loss, I'm thinking maybe deleting that file may have disrupted the boot cycle but that's just a guess.

Apologies for the long post, I just wanted to try and cover as many bases as possible, I am new to Mac computers so any suggestions would be very appreciated!