If you have a program like FindCD or what ever it's called in the IDEfix software, then try to run this.
It should tell you what device driver and unit number your CD drive has. Edit the file for your CDROM which is placed in Devs:DOSDrivers. Mine is called CD0 and CDR. In this file there should be a line where the device driver should be entered, and below there should be a line for the unit number. Set these lines to the values of the program, and try to reboot. Hopefully the error requester is gone

Good luck.
EDIT:
The error requester means that either the mountfile in Devs:DOSDrivers can't find the device driver or the unit number is wrong. Could also be a problem with the jumper settings of the CD drive.
Primary IDE cable, master, would be unit 0
Primary IDE cable, slave, would be unit 1
Secondary IDE cable, master, would be unit 2
Secondary IDE cable, slave, would be unit 3
At least on my controllers....