Let's face it - Windows 10 may not be for everyone.
It might be incompatible software, hardware or any other number of things that is not liked but bottom line is they want to go back to the operating system they upgraded from.
Well that is easy enough to do in Windows 10 and you have up to 30 days to make the decision to revert back to your former OS.
Once those 30 days are up then you will be forced to reinstall your old OS from scratch.
Here is how you revert to the previously installed OS.
1. Go to Settings>Update &security>Recovery.
2. Look for the Go back to Windows XX entry which will say either 7 or 8.1 depending on your former OS.
3. Click on Get started and follow the prompts to go through the restoral process.
Once it is complete you will find yourself in the familiar confines of your past operating system.
Take note - if you previously cleaned up after your Windows 10 install by using the Disk Cleanup tool and removed the old Windows installation files this option will not be available.
This process is the same for Windows 7 except the entry will say Go back to Windows 7 instead of Windows 8.1.