Dell Vostro 400 Owner's Manual page 139

Align the tip of a Phillips screwdriver with the slot on the break-away metal
plate and rotate the screwdriver outwards to break and remove the metal
plate.
Replacing the Floppy Drive Panel Insert
2
1
1 drive panel insert (optional) 2 back of the computer
Align the drive panel insert along the edges of the empty slot for the floppy
drive and push the panel insert.The drive panel insert is locked in place.
NOTE:
To comply with FCC regulations, it is recommended that you replace the
drive panel insert whenever the floppy drive is removed from the computer.
139
Removing and Installing Parts