Dell Dimension 2100 System Reference Manual page 68

1. If possible,
enter the system setup program
screens by pressing the <Print Screen> key before you turn off the
computer because you will have to restore the configuration information
after the system board is replaced.
2.
Remove the computer cover
3.
Remove the power supply
4. Disconnect any cables connected to cards, and
5. Disconnect all internal cables from the
6.
Remove the heat sink assembly
7.
Remove the microprocessor
8.
Remove the memory modules
.
.
system board
.
.
.
1 System-board retaining
clip
2 System board
3 Standoffs
and print the system setup
remove these cards
.
.