How can I perform a clean install after the Windows 10 upgrade?
Windows 10 automatically activates online when you upgrade your product to Windows 10. This allows you to reinstall Windows 10 again at any time, without having to purchase a license.
You can use the Microsoft media creation tool to make bootable media to reinstall Windows 10. You can choose to make a clean installation, or perform the upgrade again.
Select the option "I'm reinstalling Windows 10 on this PC," if you are asked to insert a product key. The installation will continue, and Windows 10 will reactivate your existing license.