Dell Precision T7400 (Late 2007) - Manual (Page 277)

Adding and Replacing Parts 277
15 Slide the system board assembly toward the front of the computer chassis
to release the tabs on the computer chassis from the slots on the system
board pan.
16 Lift the system board assembly from the computer.
17 Place the system board assembly that you just removed next to the
replacement system board.
Replacing the System Board
1 Transfer components from the existing system board to the replacement
system board:
1 tab 2 system board assembly
1
2