Dell Dimension U7021 Owner's Manual page 112

If the drive door is open and it is opened too far, instead of breaking away from the computer in one
piece, the drive door may disassemble into several smaller pieces. If the drive door disassembles:
1 If necessary, reattach the door hinges to the door bracket. Ensure that the hinge tabs are away
from the door bracket.
2 Attach the door bracket/door hinge assembly to the door, starting with the lower part of each
door hinge.
3 Attach the drive door to the computer, starting with the bottom bracket hinge.
112
Removing and Installing Parts
hinge tab
door hinges (2)
door bracket/door
hinge assembly
door
door bracket
lower part
of the door
hinge