Asus P4P800 SE - Manual (Page 33)

ASUS P4P800 SE motherboard 2-11
2.3.4 Connecting the CPU fan cable
When the fan, heatsink, and the retention mechanism are in place,
connect the CPU fan cable to the connector on the motherboard labeled
CPU_FAN.
3. Push down the locks on the retention mechanism to secure the
heatsink and fan to the module base.
When secure, the retention locks should point to opposite directions.
Do not forget to connect the CPU fan connector! Hardware monitoring
errors may occur if you fail to plug this connector.
CPU Fan Connector
(CPU_FAN)