When migrating various physical servers to virtual machines you may have issues with the original hardware – still hanging around. This can manifest itself in the complaint when you to try to configure a new virtual network card with the same ip address as the original physical hardware. The system may well complain that a card exists with those settings already. So you open device manager and view hidden devices but no sign of the offending card.
So the gotcha ?
Device Manager displays only non-Plug and Play devices, drivers, and printers when you click Show hidden devices on the View menu. Devices that you install that are not connected to the computer (such as a Universal Serial Bus [USB] device or “ghosted” devices) are not displayed in Device Manager, even when you click Show hidden devices.
WORKAROUND
To work around this behavior and display devices when you click 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 at the same command prompt, and then press ENTER:
start devmgmt.msc
So now you can dispose of the offending article