When you type for example "runas /user:administrator regedit" you can run regedit under the administrator user account. This is handy if you're not member of the of the administrator group.

1. Start -> Run and type cmd and click OK.
    
2. Type: runas /user:administrator regedit (see picture 1).
    

   Picture 1

3. Type exit to close the Command Prompt box.