HP ProOne 600 G3 21 inch All-in-One Business PC Hardware Reference Manual page 48

6. Align the new optical disc drive with the opening in the side of the computer. Push the drive in firmly
until it snaps into place.
NOTE:
7. Install the hard drive.
For instructions, see
8. Install the access panel.
For instructions, see
42 Chapter 3 Hardware repair and upgrade
The optical disc drive can be installed in only one way.
Installing a 2.5 inch hard disk drive on page 40
Replacing the computer access panel on page 29.