From Knoppix FAQ:
Q: My computer won't boot from CD. What should I do?
A: Look in your computer's BIOS to see whether it's set to boot from CD
(on most computers you need to push the "delete" key during the RAM test).
If this is already set, your computer may not be able to read the CD (some
notebooks have problems with black-coated CD's, for example). Some
computers will only use the new BIOS settings after a hard reset. If your
computer doesn't support booting from CD, you can create a boot floppy
using the "rawrite" program in the "KNOPPIX" directory on the CD.
Last time I've used rawrite was with Mandrake 9.0. Pretty easy with gui