v  Make  sure  that  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  that  all  of  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”  on  page  68 
v  “Reading  or  writing  the  ECA  information”  on  page  68
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  1.71  or  later,  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  of  each  device  in  your  computer  is 
displayed;  the  serial  number  of  the  system  unit  is  listed  as 
follows: 
v  20:  Serial  number 
Write  down  that  number. 
Note:  The  serial  number  of  the  system  unit  is  also  written 
on  the  label  attached  to  the  bottom  of  the  computer. 
After  you  have  replaced  the  system  board,  restore  the 
serial  number  by  doing  the  following: 
1.  Install  the  ThinkPad  Hardware  Maintenance  Diskette 
Version  1.71  or  later  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.
FRU  replacement  notices 
ThinkPad  T40/T40p,  T41/T41p,  T42/T42p  Series  67