Sounds not too difficult. There seem to be two options.
1) you use AsimCDFS to access cdroms. Look in the user-startup, there should be a line starting with ´mount´ and then at the end something like ´CD0´ or ´CD1´. Those CD0 or CD1 can be found in SYS:Storage/Dosdrivers. You can edit them with DirOpus if you want to or just delete the line in the user-startup. That way the computer won´t try to mount something that isn´t there ...
2) you use AmiCDFS or AllegroCDFS. In that case there is no line in the user-startup, but the CD0 or CD1 or whatever the cd was called is now to be found in SYS:Devs/Dosdrivers. Everything that is in that directory will be mounted on startup, so if you don´t want the cd to be mounted then you have to remove the file (with the icon) ...
Let me know if it helps ...
