Why do you want to delete anything ?
Check the CD0 mountlist and post the error message that appears when you enter Mount CD0:.
If there is no error message, enter Dir cd0: and post the error message.
If there still is no error message or the message is "no disk in drive" enter DiskChange CD0:. Does it read the CD ?
If Dir CD0: works and the only problem you have is the missing icon on the workbench desktop, check that the def_cd0.info file in envarc: and env: is a proper icon file of type Disk (load it into IconEdit and check the Type menu).
Bye,
Thomas