NOTE: Please be aware the Windows.old folder located at the root of the local disk where Windows 10 is installed will be deleted after 30 days automatically. The Windows.old folder is used to facilitate the rollback. So please perform any rollback within 30 days or this option will no longer be available. Otherwise, create a backup before upgrading to Windows 10.
See links to resources about backing up by clicking the link for the respective version of Windows you are running: Windows XP, Windows Vista, Windows 7, Windows 8/8.1
Throughout the history of Windows revisions, Microsoft has included an option to uninstall the operating system when you upgrade to a newer version. My recollection of this capability goes back to Windows ME which included the option to uninstall the operating system and restore to a previous version of Windows (I was running Windows 98 SE at the time). Microsoft has supported this functionality in its NT based versions of Windows too, albeit not in a seamless way. The ability to restore a Windows 8.1 installation to Windows 7 required knowing some command line operations that in some instances didn’t guarantee the process would go according to plan. With Windows 10, it seems Microsoft has listened and has provided a welcome option to its recovery tools to make it easy to uninstall Windows 10 and go back to your previous version of Windows. This option can be handy for diagnostics purposes, trial and error or to simply go back to a previous version of Windows that works better with your PC.
Please keep in mind, this only works with Windows 7 and later. Because prior versions of Windows such as Windows Vista and Windows XP can only migrate to Windows 10 through a custom install, the command line operations remain your best choice if you do decide to go back. Also keep in mind, if you do a custom install over Windows 7 or later, the Rollback option is not available. This only works if you had done an in place upgrade from Windows 7 or later.
Start by opening Settings – Click Start > Settings or type Settings in the search bar and click it or press Windows key + i
Click Update and Security
Click Recovery then click Get started under Go back to Windows 7 or Windows 8/8.1 (depending on the previous version you running)
Here you can make multiple selections why are going back to your previous version of Windows along with additional details or you can choose just one and click Next.
As noted, any configurations made to Windows 10 since upgrading will be lost, so if you installed new programs or hardware drivers or made personal settings, those will be deleted.
Make sure you have your password ready to sign into your old version if you had been using one. Click Next
The process can take a while depending on the amount data, applications and settings. Click Next
Click Go Back to begin the process.
Windows 10 will Restart
This will be your screen throughout the recovery process.
When the process is complete, you will be booted into your previous version of Windows environment.
If you cannot load the Windows Desktop, you can initiate a Rollback using the following method:
Log out and go to the sign in screen.
Hold down the shift key on your keyboard while clicking the Power button on the screen
Continue to hold down the shift key while clicking Restart
Continue to hold down the shift key until the Advanced Recovery Options menu appears
Click Advanced options
Click Go back to the previous version of Windows
How to: upgrade from previous versions of Windows using Windows 10 ISO file
Get started with Windows 10