Dell D31M Owner's Manual page 120

Steps
1. Remove the (#6-32) screw that secures the front I/O-bracket to the chassis.
2. Slide and remove the front I/O-bracket from the chassis.
3. Disconnect the power and HDD cables that are connected to the system board and unroute them from the routing guides on
the chassis.
120 Removing and installing Field Replaceable Units (FRUs)