Dell Dimension 2100 System Reference Manual page 57

To remove the primary hard drive:
1.
Remove the front panel
2.
Rotate the power supply
3. While holding the power supply, place the computer in the upright
position.
4. Remove the two screws securing the hard drive to the front of the
computer frame.
5. Release the clip that secures the drive to the computer frame, and
rotate the drive out of the computer.
6. Disconnect any cables attached to the drive.
7. Remove the existing drive from the bay.
To reinstall the primary hard drive.
NOTICE: When you reinstall the hard drive, make sure that the control
panel wires are notcaught underneath the hard drive.
1. Orient the new drive with its circuit board facing the front of the
computer frame.
1 Screws (2)
2 Clip
3 Hard drive
.
away from the system board.