Are you actually getting the command prompt window to open?
If so did you do so as administrator?
To do so you must first,
Click "Start", then type in the search programs and files box:-
You will then see the icon (Small black square) and cmd.exe at the top of the list, you must right click on that line and in the dialogue box that opens click on "Run as Administrator" you may get the security window asking if you want to allow the program etc, just click yes. If the DOS like Administrator cmd black window appears, try typing the ipconfig and click the enter key.
Let us know if that gets you there.