The Cdrom.BackingType enumerated type defines the valid backing types for a virtual CD-ROM device.
ISO_FILE : Virtual CD-ROM device is backed by an ISO file.
HOST_DEVICE : Virtual CD-ROM device is backed by a device on the host where the virtual machine is running.
CLIENT_DEVICE : Virtual CD-ROM device is backed by a device on the client that is connected to the virtual machine console.
Enumeration: CLIENT_DEVICE, HOST_DEVICE, ISO_FILE,