[2005] Drawing a semi transparent box over form

Have you ever seen those websites, when it requires input from you, that blocks everything except the input boxes with a semi-transparent box. I am wanting to do that but not sure what control I can use or if the suggested method is GDI+, how do I do that? I would like to use a png image that is 50% transparent.

Thanks for any help given

Use a seperate form to get your input and set the form Opacity as 50%