[ale] Making a bootable CD

[bdowd at dentfirst.com (Brian J. Dowd)]

I *must* be missing something...
downloaded several bootable .iso's and burned them over to CD's.
The CD's won't boot. (Yes, the CD drive is the first listed in the BIOS 
setup, and, in fact,
with the hard drive removed the boot loader tells me that the loaded
CD "doesn't contain a bootable image".)

I've tried downloads of Ubuntu 5-10's .iso, LFS-LiveCD's .iso
and I'm getting nowhere. Is there some sort of a bootable flag?
What am I missing?

-B