How to take screenshots without getting shadow etc.

How can i avoid getting the shadow around a window when i take screenshots?

I just want a clean screenshot without adding shadows and extra space 
around the window etc.

The screenshot tool i tried does not seem to be able to take screenshot 
of window without shadow even when i try to turn it off.

In some help files both the width and height is set and it can be hard 
to get the exact dimensions as the original image.