How to Switch off a second monitor

I wanted to switch off my second monitor on my Windows 7 Home Premium PC, so that I could connect in to my dev PC, using VNC on a Chromebook.

If I keep an extended desktop on the dev PC, then there is a lot of screen to scroll across on the Chromebook.

I wanted to preserve the settings for the second monitor, so that I did not have to spend a lot of time, re-configuring the second monitor to be just the way I liked it when I started using it again.

The answer turned out to be really simple.

How to turn off your second monitor in Windows 7, without losing the settings for it :

Windows key  + p
Change from "Extend" to "Duplicate" in the onscreen dialog.
Power off the second monitor.

To returnback to the original settings, simply
Windows key + p
Change from "Duplicate" to "Extend"
And remember to switch the monitor back on!  :-)