I'm trying to use cd instead of 'a' drive for virus scan in case of
emergency.  Typically, one starts computer with start up disk and then uses
the antivirus program afterward by changing disks in the 'a' drive.  
When starting with startup disk there is an option for starting with cd
drive support which I select.  However, my computer started in this manner
does not recognize either of my cd drives, even though it assigns a drive
letter to one of them (drive e becomes drive f when start up disk assigns a
drive letter to the temporary directory it creates).
Is there anyway that I can use my cd drive to scan for viruses in the event
that I need an emergency start some day?