Dell OptiPlex 390 (Mid 2011) - Manual (Page 32)

5. Lift the heat sink assembly upwards, and remove it from the computer. Lay
the assembly with the fan facing downwards, and with the thermal grease
facing upwards.
6. Press the release lever down and then move it outward to release it from
the retention hook that secures it.
7. Lift the processor cover.
8. Lift the processor to remove it from the socket and place it in an antistatic
package.
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