G4 Imac problems

Imac only goes to spinner on boot,then turns off.
Hardware check shows no hardware problem.
Software install disc results in window saying "Power button off and restart"
Only used as music server because of iconic looks.
Thinking of getting Tiger os, cheap from ebay
Any ideas?
Alternative is to change to PC server out of site

Overheating is a possibility. Have you had a look inside for dust build up?

As it is at least 13 years old it could be one of a number of components failing, overheating as suggested by TM or could just be the OS getting in a tizz. A hardware check may not show up issues - it may require a soak test over a period of time to find out what is wrong.

Couple of possible suggestions here and here.

(resetting PMU, PRAM and NVRAM)

Thanks everyone for replies.
As unit was working fine until switched off 3 weeks ago. Probably not overheating, fan works.
PRAM appears last resort.
Maybe try external dvd drive first, if unit will see it.
or replace internal unit.

Resetting the PRAM, as Bill suggests, is a totally harmless procedure. It's always recommended when a Mac is behaving starngely, so a first resort rather than a last one.

I�ve got one of these myself. The hard drive failed a while back and I swapped it for a ssd I had knocking about. The dvd also went and I did the same. If you have a FireWire external drive you can start up from that and use disk utility to check the internal drive. Best guess it�s that that�s went.
There�s disassemble videos on macfixit and it�s not for the faint hearted but it�s probably fixable. Wether it�s worth it is another matter, I had the parts so all I bought was thermal paste so out of nostalgia I gave it a try. The machine is almost useless as it�s incredibly slow on the Internet, file or music serving would be okay.

Macrumours suggest it is used only after all other avenues have been explored..
PMC reset and new battery fitted no change.

No firewire drive, only G4. Looks better on display than PC.
Cheaper to replace unit than change drive
DVD drive works as Hardware checks disk works and all hardware passes..
See if I can find cheap retail Tiger software as last spin of dice. Will then have disk utilities to check drive
your diagnosis probably right

In reply to a post by flippery:

Macrumours suggest it is used only after all other avenues have been explored.

Quite a few people say that, and they do have a good reason- it very seldom makes any difference, those systems rarely give trouble!

It depends on your preferred approach to fault-finding. Some prefer to try the most likely things first, others prefer to try the easiest. And resetting the PRAM etc is dead easy

(At least, it is on later Macs, not sure about the G4)