Devices that have been installed on a system but are not currently available are referred to as "phantom devices". These devices are not usually displayed in the device manager, but can be made to be displayed as though they are attached. This allows device properties to be changed or devices to be uninstalled via Device Manger even though the device is not physically connected to the PC.
To display phantom devices in Device Manager, a new system variable is required. Open "Control Panel > System" then select the "Advanced" tab and click "Environment Variables". In the System Variables section (NOT THE USER VARIABLES SECTION), click "New..." to display the following window:
Create a new System Variable called "DevMgr_Show_NonPresent_Devices" and set the value to 1, then click OK.
Open the Device Manager ("Control Panel > System" then select the "Hardware" tab and click "Device Manager
", or "Control Panel > Device Manger" in Vista) and select "View > Show Hidden Devices". Device Manager will then show all hidden and phantom devices available on that PC as shaded.