HP ProOne 600 G3 21 inch All-in-One Business PC Hardware Reference Manual page 40

If your computer model is a ProOne 400, place the EMI shield onto the chassis and use a flat blade
●
or Torx screwdriver to fasten the screws to secure the EMI shield.
7. Install the access panel.
For instructions, see
8. Turn on the computer. The computer automatically recognizes the additional memory when you turn on
the computer.
34 Chapter 3 Hardware repair and upgrade
Replacing the computer access panel on page 29.