Dell Precision T3400 (Late 2007) - Manual (Page 259)

Adding and Replacing Parts
259
7 Remove the system board screws.
8 Pull up on the two tabs, slide the system board assembly toward the front
of the computer, and then lift the assembly up and away.
9 Place the system board assembly that you just removed next to the
replacement system board.
1 system board 2 screws (8)
1 2