You may be logged onto a PC in a domain environment (or other) and you don’t have admin rights but need to make a change in device manager that requires admin rights, this is a very simple issue to resolve, and one that I used myself today on Windows 7.
1. Open a command prompt as an administrator, Right click “Command Prompt” and click “Run as Administrator.
2. Type devmgmt.msc
3. This will now open Device Manager as an administrator.