from http://blogs.msdn.com/tims/archive/2006/09/18/windows-vista-secret-1-open-command-prompt-here.aspx
Right-click on any folder on your Windows Vista machine while holding down the shift key. You’ll see an extra context-sensitive menu item there: Open Command Prompt here. Just click on this menu and a command window will open with the current working directory set to the folder’s actual location.