HP Compaq Presario,Presario CQ42-121 Maintenance And Service Manual page 76

9. Release the ZIF connector to which the power button board cable (4) is connector and
disconnect the cable from the system board.
10. Remove the Phillips PM2.5×6.5 screw (1) from the top cover, disengage the rear edge of the top
cover (2) from the base enclosure, and then remove the cover from the computer (3).
Reverse this procedure to install the switch cover.
66 Chapter 4 Removal and replacement procedures ENWW