HP 79XXY Owner's Manual page 26

Note:
The second nub (A) is on the other side of the
drive cage (not pictured).
2 Align the track (C) on the drive cage with the
guide (D) on the stationary drive cage.
D
3 Push the removable drive cage firmly against
the stationary cage as you rotate the
removable drive down into position.
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hp pavilion home pc
C
4 To make sure that the cage is locked into
position, grasp the drive cage and pull up
forcefully.
Note:
If you are able to remove the drive cage without
pressing the release tab, you didn't properly
align the track with the guide. Repeat steps 1–4
above.