Dell XPS 17 (L701X, Late 2010) - Manual (Page 127)

System Board 127
NOTE: After you have replaced the system board, enter the computer Service Tag
into the BIOS of the replacement system board.
23 Enter the service tag (see "Entering the Service Tag in the BIOS" on
page 127).
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 <F2> during POST to enter the system setup program.
4 Navigate to the security tab and enter the service tag in the Set Service Tag
field.