The Win Viewer is a simple program that lets you 'cut' a window. You select an area and the whole window apart for that area will go invisible. The left over area will be given a small title bar which allows you to move it around, change the transparency and disable the window. This is useful for watching movies while doing other things and keeping an eye on downloads or progress of something.
I have uploaded a zip folder with the source code ( AutoHotkey ), the executable, 2 gifs showing its use and a pdf explaining how to use it.
As noted in the pdf, some windows dont fully work and there are known bugs. I will work on it if people seem interested.