Dell Precision Workstation 370 User's & Service Manual page 80

b. On the retention base locate the tab opposite the power supply. Press on the retention base tab until the heat
sink pops up slightly.
c. Press out on the second retention tab while lifting the heat sink up and out of the retention base.
NOTICE: Lay the heat sink down on its side.Do not touch or remove the thermal grease on the bottom of the heat
sink.