Dell Dimension XPS R Series Service Manual page 48

After you have removed the computer cover and the bezel, remove the front-
panel insert for the bay you plan to use. From the back of the bezel, as shown
for the mini tower chassis in Figure 4-3, press the release tab to the side,
rotate the insert toward you, and remove it from the bezel. For mini tower
computers, you must remove the upper insert to remove the lower insert.
tabs (2)
release tab
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4-4 Dell Dimension XPS R xxx Systems Service Manual