Viewing Hidden Devices
Device Manager lists the devices that are installed in the computer. By default, certain devices aren't shown in the list. These hidden devices include:
Devices that have the device node (devnode) status bit DN_NO_SHOW_IN_DM set.
Devices that are part of a device setup class that is marked as a NoDisplayClass (for example, printers and non-PnP drivers)
Devices that were physically removed from the computer but whose registry entries weren't deleted (also known as non-present devices or phantom devices).
Starting with Windows 8 and Windows Server 2012, the Plug-and-Play Manager no longer creates device representations for non-PnP (legacy) devices. Thus there are no such devices to view in the Device Manager.
Users should never have to view non-present devices because a non-present device should not have their attention and should not cause any problems. If a user has to view your device when it is not present, there is likely a problem with your driver design. However, during testing, a developer might have to view such devices.
To include hidden devices in Device Manager display, select View and select Show hidden devices.
Prior to Windows 8, to view non-present devices, you must set the environment variable DEVMGR_SHOW_NONPRESENT_DEVICES to 1 before you open Device Manager, then open Device Manager, and on the View menu, select Show hidden devices.
To permanently set the user environment variable DEVMGR_SHOW_NONPRESENT_DEVICES to 1, use the Advanced tab of the system property sheet. After you set this environment variable, run Device Manager and select Show hidden devices.