The Screen Saver running in the window works by displaying preview of the screen saver. In order to run Screen Saver on second monitor on a Dual Monitor Windows Computer, all you need to do is specify the screen saver, move it to the second monitor by dragging the title bar (as you would drag any other windows application) and finally switch to full screen mode using menu or shortcut key combination F11.
The Screen Saver in a Box application allows to run Screen Saver in a Window which can be maximised normally or in full screen mode. Run Screen Saver on Second, Third or any other Monitor