My ASUS board (P8Z68) shows 3 items in the dialog, Microphone, Line In, and Stereo Mix. If you right click the window you should see an option for showing disabled and disconnected items. If that is not checked, it may show up when something is plugged in.
Also ask the user is they show a Realtek HD Audio Manager in the Control Panel. If that board has Realtek, it may show up if the drivers are loaded.