HP Compaq Business PC Hardware Reference Guide - Elite 8300 Series Convertible Minitower Elite 8300 Series Microtower Elite 8300 Series Small Form Factor Elite 8300 Series Ultra-Slim Desktop

Figure C-3 Removing the Smart Cover Lock Screws from the Small Form Factor
You can now remove the access panel.
To reattach the Smart Cover Lock, secure the lock in place with the tamper-proof screws.
Using the Smart Cover FailSafe Key to Remove the Smart Cover Lock 165