If you've upgraded to Windows 11 and find it's not to your liking, you can revert to Windows 10 within ten days using the built-in recovery options. Go to 'Settings > Update & Security > Recovery' and select 'Go back to the previous version of Windows 10'. After ten days, this option disappears, and you would need to perform a clean installation of Windows 10, which involves backing up your data, creating Windows 10 installation media, and reinstalling Windows from scratch.