How to reset the CMOS password on Dell Dimension Computers

Locate the 3-pin CMOS password reset jumper on the system board.
Remove the jumper plug from pins 1 and 2.
Place the jumper plug on pins 2 and 3 and wait approximately 5 seconds.
Replace the jumper plug on pins 1 and 2.

For a Diagram to locate the 3-pin CMOS password reset jumper:
Dell Dimension User Guide Online