i have never tried this knoppmyth, so i have only one solution to accessing cd-rom files. login as root (or become super user by typing su in shell console + type your root password) then you need a dir which you will use for accesing files, i suggest to create one in /mnt, but not necessary. i.e create cd so you had /mnt/cd now use command mount /dev/hd* /mnt/cd. *-means the letter a,b,c or d depending what is your cd-rom's state: hda- for primary master, hdb- primary slave, hdc-secondary master, hdd: secondary slave. some distro's need that you add 1 to end i.e. hdd1. this is the most common way to access cd-rom.
NOTE: you'll be able to access cd-rom only as root or super user this way!!