Mac won't boot from OS X CD

Hi there,

So first off, I have very very little experience with operating Macs outside of schoolwork (Photoshop and whatnot).

Anyways, I've got a friend's PowerBook G4 here that he's recently purchased (used, of course), and the last owner didn't format it/reinstall OS X, so we don't have access to the computer past the login screen, so he's asked me to reinstall OS X.

I've got the CD here (OS version 10.2.1, if that matters), and I put it in and reboot, and press/hold C while it starts up, but it just goes straight back to the login screen every time. I've tried Googling this, but it doesn't look like anyone else has had this problem, or I'm just bad at searching.

Any solutions?