Windows Forms - PNG with transparency as background

I'm working on a small personal project and I need to create a non-rectanguar window (a circle to be more precise - though that might change) that has a drop shadow. I have the round window by changing the Region property if the form with a png set as background.

The thing is the window is alised and the transparency of the PNG is not working. So the question is how do I get a a antialised window and the transparency of the background image OR the antialised circular window and a way to add the drop shadow effect to the win开发者_如何学JAVAdow.

Thanks.

You need to make a Layered Window using P/Invoke.

Here is a .Net example.