Dell Inspiron 660s Owner's Manual page 74

Procedure
NOTE:
Your computer's Service Tag is stored in the system board. You must enter
the Service Tag in the BIOS after you replace the system board.
NOTE:
Before disconnecting the cables from the system board, note the location of
the connectors, so that you can reconnect them correctly after you replace the
system board.
1 Disconnect all the cables from their connectors on the system board.
2 Remove the screws that secure the system board to the chassis.
3 Lift the system board up and out of the chassis.
1
1 screws (6)
70
System Board
2
2 system board