I'll just point out here that every single time I've run into a system that won't boot from a CD-ROM drive, it's because the CD-ROM has to be a master on one of the IDE channels. It can be a master on the secondary channel, that's fine, but with many systems, running a CD-ROM drive as a slave is the kiss of death for CD booting.

As for booting from a floppy, one approach I've used in the past is to boot a (MS|Free)DOS disk with CD-ROM drivers on it and use a copy of loadlin to boot Knoppix. The only catch is that you have to type all the boot parameters and cheat codes by hand, including the ones you don't usually see (they're in /KNOPPIX/boot/isolinux.cfg on the CD), and sometimes that exceeds the DOS command-line length limitation. But it'll do in a pinch, like when I need to boot Knoppix on my old P166 laptop that's incapable of booting from CD.