Boot from Ubuntu CD?

Help me, people.

I did something to the HD on my iBook (see signature) so I'm trying to use my Ubuntu Live CDs to get into the computer. But I can't get the iBook to boot from the CDs. I tried both the red 32 bit and yellow 64 bit CDs. When I press C, it tries to boot from the HD (to which I get a grey screen with Apple but no spinning disk). I tried to bypass HD startup by pressing Command + Alt + Shift+ Delete but that just yielded a very OS 9-looking screen with a graphics alternating between a folder with a ? and a Finder face. Then I tried Alt boot but that gave me another OS 9-ish screen with a Macintosh HD graphic but no CD. When I select Macintosh HD, it just does what it does on a normal bootup: grey Apple, no spinning disk.

Here are all the key combos I've tried:
C
Alt + C
Command + C
Command + Alt + Shift + Delete
Command + V
Alt


I've also reset PRAM.

Please help, guys.