Bear in mind, it does not have to be called CD0 or anthing like. It would, as Mozzerfan said, be useful to list all files in the devs:dosdrivers directory.
You could also have a look in your startup-sequence and user-startup files. There could be a "MOUNT randomlocation/randomfilename" command in there.
Also, the mountfile could be in the wbstartup drawer, with the file associated with "mount" in the icon prefs.
Also, when you do find the file (and it is there somewhere!), change the device name in both the text of hte file itself, and in the tooltypes. I'm sure one is dominant over the other, but buggered if I can remember which.