HP ProDesk 400 G3 MT Hardware Reference Manual page 22

c. If you are removing a PCI Express x16 card, pull the retention arm on the back of the expansion
socket away from the card and carefully rock the card back and forth until the connectors pull free
from the socket. Lift the card straight up then away from the inside of the chassis to remove it. Be
sure not to scrape the card against other components.
9. Store the removed card in anti-static packaging.
10. 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.
11. To install a new expansion card, hold the card just above the expansion socket on the system board
then move the card toward the rear of the chassis (1) so that the bottom of the bracket on the card
slides into the small slot on the chassis. Press the card straight down into the expansion socket on the
system board (2).
NOTE:
properly in the expansion card socket.
16 Chapter 2 Hardware upgrades
After removing an expansion card, you must replace it with a new card or expansion slot
When installing an expansion card, press firmly on the card so that the whole connector seats