Well, if you put the cleaner disk into the cdrom and the computer engages, then the cdrom will try to read the cleaner disk's type and program instructions. If the lens is terribly dirty, then the program on the cleaner (if there's one) and even the program type (usually something like an audio wav file) may not be recognised by the puter.
But then the cleaner disk (with its little lens attachment brush) is spinning the entire time the puter's trying to figure out what it is. So even if the fancy program fails to initiate, some cleaning does occur. You can, of course, repeat the cleaning process as needed. The lens brush is very soft and won't scratch.