Did you try searching for an article or anything on showing a splash screen? Because if you did you would have found quite a few. You would also likely have found out about Layered Windows which would allows you to use your PNG with it's alpha channel as the picture for your splash screen.
Overall it would have been a grand learning experience. Still, I'll at least get you started eh? As I've typed this much already.
To show a splash screen you just need to show a window with a picture on it, to have it blend with the desktop in 32bit goodness you need to use the WS_LAYEREDWINDOW style. An excellent example of both of these things can be found in this article:
I know the code is in C# but really it's only a little bit of code and it shouldn't be too difficult to understand.