Dell Precision T7400 (Late 2007) - Manual (Page 275)

Adding and Replacing Parts 275
11 Remove any components that restrict access to the system board.
12 Disconnect all cables from the system board.
13 Before you remove the existing system board assembly, visually compare
the replacement system board to the existing system board to ensure that
you have the correct part.
14 Remove the two screws that attach the system board assembly to the back
of the computer chassis.
1 screws (2) 2 processor and card fan case
1
2