Show hidden devices:
Click Start, point to All Programs, point to Accessories, and then click Command Prompt.
At a command prompt, type the following command , and then press ENTER:
set devmgr_show_nonpresent_devices=1
Type the following command a command prompt, and then press ENTER:
start devmgmt.msc
Troubleshoot the devices and drivers in Device Manager.

NOTE: Click Show hidden devices on the View menu in Device Managers before you can see devices that are not connected to the computer.
When you finish troubleshooting, close Device Manager.
Type exit at the command prompt.

Note that when you close the command prompt window, Window clears the devmgr_show_nonpresent_devices=1 variable that you set in step 2 and prevents ghosted devices from being displayed when you click Show hidden devices.
If you are a developer or power user and you want to be able to view devices that are not connected to your computer, set this environment variable globally:
Right-click My Computer.
Click Properties.
Click the Advanced tab.
Click the Environment Variables tab.
Set the variables in the System Variables box.

 

the set devmgr_show_nonpresent_devices=1 command does not work on Windows 2008 (or Vista, Windows 7, or Windows 2008 R2).  To see and remove ghost NICs from Windows 2008, and environmental variable must be defined.  To set the variable, open Server Manager from the Windows Start Menu.  Highlight ‘Server Manager (%SERVERNAME%)’ in the left-side tree-view pane.  Click ‘Change System Properties’ in the right-hand pane.  Switch to the Advanced tab and click ‘Environment Variables.  Create a new System variable by clicking the New button.  The Variable name should be ‘devmgr_show_nonpresent_devices’ and the value should be ’1′ as pictured below.

http://vmtoday.com/wp-content/uploads/2009/11/EnvVariable.JPG

Click OK to close out of any open Windows.  A reboot is not necessary for the variable to take effect, although you may have to close out of all open Device Manager Windows and then reopen devmgmt.msc.  Click View | Show Hidden Devices and remove the ghost NIC as described above.  A quick reboot after I removed the ghost NIC from the domain controllers and all Active Directory, DNS, DHCP, and WINS services immediately began operating normally.  This second issue is more of a Microsoft problem in my opinion, and has been around for some time.