windows 7 - How do I resolve the error "The local device name is already in use."?

I try to map a network resource to my local device.

I receive the following error: The local device name is already in use.

I have the problem to find which purpose the device is used for. I try a command net use and do not see it in the list, therefore, it is not mapped to a network resource.

Does anybody know how to see the list of all used devices in Windows 7?