For some reason in Windows Vista, even if you’re signed in as an administrator, you’re still required to use the command “Run as Administrator” from within Vista sometimes. This holds true for the functions that are available in the Command Prompt – you won’t have access to all functions unless you have opened the Command Prompt with the “Run as Administrator” specification. Here’s how you do it:

1. Click on the Start button.
2. In the search box, type in cmd or Command Prompt – Do not press enter.
3. cmd.exe or Command Prompt will show up in the search results (depending on what you searched for).
4. Right click cmd.exe (or Command Prompt) in the search results and select “Run as Administrator”.
5. Enter the administrator credentials when prompted.