I'm not sure because I don't own an iBook, but here are some generic troubleshooters to try:
1. Try starting up from the installation CD. Open the CD slot (This can be done by holding the mouse (touchpad?) button down while starting up), insert the disk, and restart while holding down the C key. If that doesn't work, hold down the option key while starting up and select the CD from the menu that appears.
2. Start up with the command, option, O, and F keys held down. A white screen with black text should appear. (If not, then yes, it probably is toast.) When the screen appears, type "reset-nvram". You may be prompted for your Open Firmware Password. If so, enter it. (If you can't remember it, then there is no way to fix your computer other than waiting for a couple of years for the on-board battery to die.) Next, type "reset-all". then, restart the computer and try step 1 again.
Apple has excellent documentation on Open Firmware Password. Make them explain it to you; I'm making this post way too long. If no menu appears when you hold down the option key or nothing happens when you hold down cmd-opt-O-F, then something's happening that I can't fix.
Hope this helps!