For Windows 10, press Windows button + P.
It will pull up a windows on the right side of the screen, from there, click on “PC screen only” to disable the second and third monitor.
If you want to switch back and enable all the monitors, do the same but click on “Extend”.
In Windows 7, this was possible by using shortcuts inside AMD catalyst center for those that had Radeon graphic cards. With the new drivers, the shortcuts are gone, missing.