Panasonic CF-W4 Series Reference Manual page 66

DVD-ROM & CD-R/RW Drive
66
When the power to the DVD-ROM & CD-R/RW drive is turned off, the message "The
'USB Mass Storage Device' device can now be safely removed from the system" will
appear, but the DVD-ROM & CD-R/RW drive is an internal device, so it cannot be
removed.
If the drive power is turned on after starting up a software application while the drive
power is off, the software application may not recognize the drive. If this happens, exit
the software application, and then start up the application once more after checking to
make sure that the drive power is on.