Dell Dimension 2100 System Reference Manual page 54

To remove the upper 3.5-inch drive plate and install a new drive:
1.
Remove the front panel
2.
Remove the 3.5-inch front panel insert
3.
Rotate the power supply
power supply, place the computer in the upright position.
4. Remove the metal plate covering the bay by using a screwdriver to pop
out the metal plate from the left or right side of the computer frame.
5. Remove the extra rails from the inside front of the computer frame.
6. Install the rails on the sides of the drive.
The rails are marked "L" for installation on the left side of the drive and
"R" for the right side of the drive.
7. Slide the drive assembly into the drive bay.
8. Connect a power supply cable and drive cables to the drive.
Lower 3.5-Inch Floppy Drive
1 Drive bay plate
.
.
away from the system board. While holding the