private void killAllWindows()
 {
     if (pupScreens != null)
     {
         foreach (PupScreen pupScreen in pupScreens)
         {
             pupScreen.PropertyChanged -= PupScreenPropertiesChanged;
             pupScreen.Window.UnauthorizedActivation -= UnauthorizedActivationOfPupScreen;
             pupScreen.Window.Dispose();
         }
         pupScreens.Clear();
     }
 }