This article contains info on how to create and use installation media to reinstall Windows 10, and some tips on getting started.
Back up your personal data and files to an external hard drive, USB thumb drive, SD card, or cloud location (such as OneDrive) before you begin to reinstall Windows 10.
Where to find Windows 10 reinstallation media
Tips to keep in mind before you reinstall Windows 10
You don't need a product key if Windows 10 was already activated on your device before you reinstall it. If you made a significant hardware change to your PC (such as replacing the motherboard) before reinstalling Windows 10, see You can reinstall Windows 10 after making a significant hardware change below.