Compaq Deskpro EX User Manual page 40

When you install an expansion card, make sure you press firmly on the card so
that the entire connector seats properly in the expansion card slot.
10. Replace the screw at the top of the expansion slot.
11. Replace the computer cover.
12. Connect external cables to the installed card, if needed.
13. Reconfigure the computer, if necessary.
4-16 Removal and Replacement Procedures