HP Compaq Presario,Presario C770 Maintenance And Service Manual page 88

Remove the heat sink (2).
3.
NOTE: The thermal material must be thoroughly cleaned from the surfaces of the system board (1)
and (2) and the heat sink (3) and (4) each time the heat sink is removed. Thermal pads and thermal
paste must be installed on all surfaces before the heat sink is reinstalled. Thermal pads and thermal paste
are included with all heat sink, system board, and processor spare part kits.
Reverse this procedure to install the heat sink.
80 Chapter 4 Removal and replacement procedures