Acer Altos R720 Series - Manual (Page 74)

3 System upgrade 64
Note: Make sure the board seats securely into the plastic retainer
at the bottom of the opening in the backplane board.
7 Install a hot-plug HDD into the sixth HDD bay. See “To install a
HDD” section on page 49 for installation instructions.
8 Observe the post-installation instructions described on page 36.