The file that Knoppix generates to tell itself which drives are available and under what circumstances is /etc/fstab -- so a good idea would be to look at /etc/fstab in an editing application and either 1) figure out what needs to be done to fstab to make your CD drives available using what you know already or 2) reply including the contents of your fstab file so people can look for something going wrong and help you fix it!