Dell Dimension 2100 System Reference Manual page 56

To remove the 5.25-inch 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. Disconnect the power and interface cables from the back of the drive.
5. Press the two drive-release rail tabs, and slide the drive out of the drive
bay.
Before you install the new drive, install the drive-release rails on the sides of
the replacement drive.
Hard Drive
1 Drive-release rail tabs (2)
.
away from the system board.