Installing 10.5 on iBook G4 = Fail. Help with booting?

[z11111]

So I have my Leopard DVD installer that I want to put on my iBook, but I can't, for many reasons.
1. My built in Combo Drive won't recognize the installer DVD, so I can't install that way.
2. The only drive I have that will recognize the DVD is a external USB DVDRW drive, and after lots of research, I am already well aware that you cannot boot a G4 (let alone any PPC) from USB.

So what can I do? Can I burn some sort of image to a CDR that will let me boot from my USB drive? I read about modifying firmware so a G5 will boot from USB, but I'm not sure if this will work. I mean, in a worse case scenario I can go out and buy a firewire cable and boot in Firewire Target Disk off a friend's Mac, but I'd like a simpler solution if possible.

Thanks

[Giaguara]

Which iBook? Specs? CPU speed, RAM amount, HD size, model or at least year?
Does it meet system requirements?
Is it a black or a gray Mac OS X install disc? If it's gray forgettdaboutit, those are CPU specific just like the discs that shipped with your iBook...