title: Collect all active window class names
body: <p>Many programs (True Transparancy and others) can get all active or running in background window class names like this one:</p>
  
  <p>Delphi 7 Object Inspector name is <code>tpropertyinspector</code>
  <br>
  Opera main window class name is <code>operawindowclass</code><br>
  etc.</p>
  
  <p>So how to get any opened window class name in Delphi?</p>