There is never a lack of unforeseen situations that force us to retire for a while leaving our computer in the sight and patience of anyone, well one more option to maintain our privacy is Magic Boss Key; an excellent free utility for Windows that effectively and safely hides windows, taskbars and desktop icons.
By default the program comes in English but from the official site you can download more languages, I should mention that its translation into Spanish by default, including spelling is small that is why I have taken the trouble (read modesty) to make a vision downloadable translation here.
Using the program is easy either by pressing the F12 key or at the same time both mouse clicks depending on the configuration you have chosen.
It would also be good if you made your own portable version to carry it on the USB memory as it is a very useful tool.