Dell Inspiron 14 (N4120, Early 2011) - Manual (Page 82)

82 System Board
20 Replace any cards or blanks removed from the 8-in-1 media card reader.
CAUTION: Before turning on the computer, replace all screws and ensure that no
stray screws remain inside the computer. Failure to do so may result in damage to
the computer.
21 Turn on the computer.
NOTE: After you have replaced the system board, enter the computer Service Tag
in the BIOS of the replacement system board.
22 Enter the service tag (see "Entering the Service Tag in the BIOS" on
page 82).
Entering the Service Tag in the BIOS
1 Ensure that the AC adapter is plugged in and that the main battery is
installed properly.
2 Turn on the computer.
3 Press as soon as you see the Dell logo to enter the system setup
program.
4 Navigate to the security tab and enter the service tag in the Set Service Tag
field.