Dell OptiPlex 740 - Manual (Page 201)

Small Form Factor System Board Screws
Place the system board assembly that you just removed next to the replacement system board to ensure it is identical.
Replacing the System Board: Mini Tower, Desktop, and Small Form Factor Computers
1. Gently align the board into the chassis and slide it toward the back of the computer.
2. Using the screws, secure the system board to the chassis.
3. Replace any components and cables that you removed from the system board.
4. Reconnect all cables to their connectors at the back of the computer.
5. Replace the computer cover (see Replacing the Computer Cover ).
1 desktop system board 2 screws (8)
1 small form factor system board 2 screws (6)