Asus P4B - Manual (Page 34)

2-12 Chapter 2: Hardware information
2.5.4 Removing a DIMM
Follow these steps to remove a DIMM.
1. Simultaneously press the retaining clips outward to unlock the DIMM.
Figure 2-16 Removing a DIMM
Support the DIMM lightly with your fingers when pressing the retaining
clips. The DIMM might get damaged when it flips out with extra force.
2. Remove the DIMM from the socket.