What if you upgrade to Windows 10 and then decide you just don’t like it? If you’ve upgraded from Windows 7 or 8.1, then there is a way to roll back to your previous setup and remove Windows 10 altogether, without affecting your files.
Update: the July 31st 2016 deadline for upgrading to Windows 10 has now passed, so the latest date that the below process would be possible was 30th August. If you're looking to roll back Windows 10 to your earlier operating system, this won't now be possible by following this process. It's still possible to do if you created a system image of your own to an external hard drive before you upgraded to Windows 10, but this requires different steps.
Go back to Windows 7 or 8.1
If you had enough free hard drive space when you upgraded to 10, Windows would have created a special Windows.old file that can be used to roll your PC back to the way it was before you upgraded.
To do this, click Start > Settings > Update & security > Recovery.
You’ll see an option to Go back to Windows 7 (or Windows 8.1, depending on the version you upgraded from). Click Get started under this, then follow the prompts to complete the process.
The bad news is that there’s a time limit on this method – you only have 30 days from when you first upgraded to decide whether or not you want to go back.
You can still revert, however, provided you had manually created a system image before upgrading.