Sony PCG-F420 Primary User Manual page 35

Turn off the computer.
There is a RELEASE lever on the bottom of the computer. Slide this
lever in the direction of the arrow.
Slide the drive out of the multipurpose bay.
Insert the weight saver. See "Using the Weight Saver" on page 41.
Turn off the computer.
If another device is in the multipurpose bay, remove the device. See
"To remove the floppy disk drive" on page 25 or "To remove the
second battery pack" on page 40.
Insert the floppy disk drive into the multipurpose bay with the VAIO
label facing up. Continue pushing the drive into the bay until the
RELEASE lever locks into place.