Start Up Issues ... iBook G4

I have an iBook G4, that upon start up (makes the chime noise, shows the apple, and the active circle) automatically shuts off. It never reaches the Log in screen.

I have tried to boot from the install disk ... no go.

It also has a full battery charge & is plugged in, is this my HD? or something else.

Thanks in Advance!

Most likely it will be the logic board on this machine, as they are very prone to failure sadly, especially if it's an older model.
I would suggest you try running FSCK and NVRAM/PRAM resets though, just to see if it helps, which it often does.
A search of the site will give you info on how.