Quote Originally Posted by Harry Kuhman
If your CD isn't bootable the reason is that you didn't follow the instructions ...
Sorry, I didn't mention clearly enough why I want this. I do know how to burn bootable CDs.

I'm currently creating customized knoppix-CD, and I want to support a scenario where the user of this CD doesn't know how to properly copy his/her CD, and makes a non-bootable copy to his/her friend.

Now I want that friend to be able to create a new bootable CD with what he/she has, with as little hassle as possible.
Currently I'm thinking of adding images of boot-floppies to the CD, which can be used to boot the unbootable CD, and a simple script to recreate the original iso-file with right options.