Hi. As I switch the ibook G4 on all I get is the apple symbol

Hi Baz,
This is often a sign of directory corruption on the HD. Try starting up from your installation CD (restart and hold down the C key as soon as you hear the bong - keep holding 'till the Apple appears) The CD will want to install all over again but if you look at the menu bar you should find a Utilities entry. Select Disk Utility and use to to repir the disk. Often that is all you need do. However, sometimes you get a message saying that disk repair failed or could not repair the disk. In that case you need some stronger software - and the best place to start is with diskWarrior from Alsoft. It is very good at getting almost dead disks back to life. It will inform you if there is something wrong with the disk that is making the disk itself unreliable. If it does then the HD needs to be replaced - which is a workshop job on these Macs.