Stuck on the restart your computer screen.

that's a kernel panic, which means there's probably a problem with your operating system. Use the original disks to reinstall the OS.

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Have you added memory to the machine?

If so, is the memory to the right specification?

Try SMC and PRAM reset. To do this you need to google the model number and the reset instructions. If that does not work you need to reinstall the OSX

Hold down the shift key immediately after starting the Mac. Keep holding til you see something on the screen.

Option 1:
If you restart the computer and just after it restarts if you hold down the eject key on the keyboard it should eject the disc, if not I would check to see if there is a tiny hole on the disc drive that you can stick a paper clip in - not sure if the ibook will have it but worth while checking.

Option 2:
1. Restart the computer.
2. Immediately after the startup sound, press and hold the key
combination Command-Option-O-F.
Note: The Command key has the Apple icon on it.
3. Release the keys when you see a white screen that says "Welcome to
Open Firmware."
4. At the prompt, type: eject cd
5. Press Return, then wait a few seconds. The disc drive should eject any disc that is present, and "ok" appears behind your command when the
action is complete.
6. Type: mac-boot
7. Press Return.

its grounded or short... call your technician

i have the same problemmm=[

use system restore ,,

Try resetting the PRAM by turning on the iBook then holding option + command + P + R and wait till u hear another chime. If it still freezes, it may indicate an application may be causing it to lock up hold shift after you hear the chime to boot OS X into safe boot.

Try adjusting the monitor brightness (F2). If you have an extra monitor, try connecting the mini VGA to see if it outputs a signal extenally. The videocard is onboard the logicboard....so, that is one way to process of eliminate.

Also, if you start the machine after the apple chime, hold down the OPTION key. This will prompt you as to which bootable volume to boot from. What this does though, is gives the monitor a signal before the operating system loads.....this usually eliminates the issue being software, but very seldom is no display a software issue.....

Hope this helps.