HP COMPAQ BUSINESS NOTEBOOK PC X1000 Maintenance And Service Manual page 106

Removal and Replacement Procedures
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Carefully clean any thermal grease residue from the heat sink 1
and processor surfaces 2 each time you remove the heat sink.
Apply new thermal grease to both surfaces.
Removing the Thermal Grease From the Heat Sink and Processor
Reverse the above procedure to install the heat sink.
Maintenance and Service Guide 5–23