HP ProDesk 400 G4 Maintenance And Service Manual page 44

b. If you are installing an expansion card in a vacant PCI Express x16 socket, remove the appropriate
expansion slot cover on the back of the chassis. Pull the slot cover straight up then away from
the inside of the chassis.
7. Store the removed card in anti-static packaging.
8. If you are not installing a new expansion card, install an expansion slot cover to close the open slot.
CAUTION:
cover for proper cooling of internal components during operation.
Reverse this procedure to install an expansion card. Reconfigure the computer, if necessary.
36 Chapter 4 Removal and replacement procedures
After removing an expansion card, you must replace it with a new card or expansion slot