Booting a mac Mini from cD?

[Al Puzzuoli]

Hi all,
I have a PPC based Mini, and I want to test the Ubuntu Linux live cd.  I 
downloaded the iso, and burned it to disk on a PC using Nero.  If I insert 
the disk into the Mac and restart the system, I hear the disk spin for a few 
moments, but ultimately, mac OS starts, and the cd doesn't boot.  Is there 
something I'm missing here, or is my cd just not bootable for some reason?

Thanks,

--Al