Removing CPU Heatsink plate on K8N Neo4 Platinum for Zalma..

I am looking to put a Zalman Copper 7700 cpu cooler fan/heatsink. I
have unscreweed the plastic mounting bracket from the motherboard, but
I am unable to see how to remove the backing plate on the underside of
the motherboard.

This is for a 939 socket and the Zalman has its own backing plate for
this purpose.

Thanks,
Nestor