How to get a display from one computer into a window on a second computer?
 

I need to get the entire desktop display from one computer (preferably via USB 2.0 or 3.0) into a window on a different computer. Today, I do that with a webcam pointing at the other monitor, but this is clunky and results in a low quality image. Any ideas, please?

Teamviewer works pretty well. http://www.teamviewer.com/en/index.aspx

Try a VNC solution -- most clients allow you to specify which display to show.