MWSnap is highlighting a zombie window.

I use MWSnap (http://www.mirekw.com/winfreeware/index.html) for my screen capturing. This programme has a option to capture a single window, and when activated, this mode highlights every available window.

I had been re-sizing the Control Panel window with the intention of taking a screenshot. Only wanting to have the window, I activated that option. To my surprise, there was an outline of the control panel window, of the size and shape that it had just been in before I re-sized it to the shape you seen in zombie-outline.png (taken with a camera).

I have tried to replicate this zombie window, but I could not at first, but once I found a zombie window, I could keep replicating it, by just re-sizing the window.
So I have taken a screenshot of the zombie window (see zombie-window.png).

I have tried to replicate this in WindowsXP, but I have failed.
The outline is a different colour (blue/green with black dashes), and other than the desktop area, no window is highlighted until the mouse pointer moves over the window.