title: Get the list of opened windows C#
body: <p>During the installation of any application. Generally the user was asked to close all windows before start of installation. if not the installation will stop at the middle
  and ask the user to close all opened windows.
  I was asked to add a code in a XXX application. When application is running and if user opened any other window (ex: Explore, browser, word etc..) 
  then the application should throw a window saying that you have opened the list of windows.
  I requerst you please suggest me how to start in C#.</p>