I see that you have not got any answers, and I am pretty sure it's because we all think the same. Put yourself in your user's place: What right do you have to change their machine? If they want the taskbar to be visible, then it's their choice, and you should not force another setting upon them. If you have a very, VERY good reason for having the taskbar removed, then you should ask your user to hide it, simple as that.

>how to maximize a form to cover all the screen even windows taskbar ?