With too many windows and applications open all at the same time, it can be frustrating to close each and all of them seperately. CloseAll is a useful tiny utility which when launched will close all the open applications and programs all through a single click.
Download CloseAll from here and extract it to a suitable location.
Once extracted, either make a shortcut to desktop by right clicking and selecting Send to > Desktop or pinning it to taskbar.
Do remember that when pinned to taskbar, even when clicked accidentally, it will close all applications.
Exceptions to which programs can be closed can also be made by modifying the launch parameters. To do this, right click the CloseAll desktop shortcut and append the -x parameter followed by the applications or programs which should not be closed. Take a look here for detailed explanation for the same.