HP Compaq Presario,Presario 4400 Hardware Reference Manual page 41

Computer Upgrades
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3. If you are removing an existing expansion card, remove the
screw 1 at the top of the expansion slot. Holding the card at each
end, carefully rock it back and forth until the connectors pull free
from the socket 2. Be sure not to scrape the card against the other
components.
Keep the screw that secures the expansion slot cover to the chassis.
You will need it when installing the new card.
Removing an Expansion Card
4. If you are not replacing the old expansion card with a new
expansion card, install an expansion slot cover to close the open
slot. Insert the metal slot cover in the opened slot and install a
screw to to the top of the cover to secure it in place.
Hardware Reference Guide