Set fullscreen dynamically?

[LsDefect]

I'm working on an assignment to make pong (due tonight). I'm all done, except I need to implement the option to toggle between windowed and full screen mode. I changed my bool g_bWindowed to false and got full screen, but it wouldn't render (all black, still sound). What else do I have to do to get full screen from the message loop? Lmk if any additional info is required, and thx to whoever reads this.