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v Make sure you use the correct screw. If you have a
torque screwdriver, tighten all screws firmly to the torque
shown in the table. Never use a screw that you
removed. Use a new one. Make sure the screws are
tightened firmly.
Retaining serial numbers
This section includes the following descriptions:
v “Restoring the serial number of the system unit”
v “Retaining the UUID”
Restoring the serial number of the system
unit
When the computer was manufactured, the EEPROM on
the system board was loaded with the serial numbers of
the system and all major components. These numbers
need to remain the same throughout the life of the
computer.
If you replace the system board, you must restore the
serial number of the system unit to its original value.
Before replacing the system board, save the original serial
number by doing the following:
1. Install the ThinkPad hardware maintenance diskette
version 1.62, and restart the computer.
2. From the main menu, select 1. Set System
Identification.
3. Select 2. Read S/N data from EEPROM.
The serial number for each device is displayed. Write
down the serial number of the system unit, designated as
follows:
20: System unit serial number
After you have replaced the system board, restore the
serial number by doing the following:
1. Install the ThinkPad hardware maintenance diskette
version 1.62 and restart the computer.
2. From the main menu, select 1. Set System
Identification.
3. Select 1. Add S/N data from EEPROM.
Follow the instructions on the screen.
Note: The serial number of the system unit is written on
the label attached on the bottom of the computer.
Retaining the UUID
The Universally Unique Identifier (UUID) is a 128-bit
number uniquely assigned to your computer at production
FRU replacement notices
ThinkPad T20, T21, T22 and T23 series 57