The Windows 10 upgrade process drags old files, settings, and programs from your previous Windows system to your new one. Microsoft allows you to get an entirely fresh system by performing a clean install, but the activation process can be a bit confusing.
This is also useful if you’ve purchased a new Windows 10 PC and it includes manufacturer-installed bloatware you don’t want. Or, you may need to perform a clean install on a computer without an existing Windows system after installing a new hard drive.
Note that you won’t be eligible for the free “Windows DVD Player” app offered to users of Windows Media Center if you perform a clean install. However, you can always