HP Pavilion xt800 - Desktop PC Manual page 13

2 Disconnect the modem/phone cable.
3 Disconnect the power cord and all other
attached cables (such as the keyboard,
mouse, and monitor).
4 Remove the side panel (see "Removing the
Side Panel" on page 3).
5 Gently lay the computer on its side.
6 To release the add-in card bracket (A),
push down on the release mechanism (B)
as you pull the bracket.