Do in-place upgrade or clean installation. Don't not re-format hard disk when you install a new windows.  www.technig.com/windows-10-in-place-upgrade
Hi there, since when I've upgraded Windows 8.1 to Windows 10, my notebook seems much more slow. I would like to know if there's a way to do a clean installation of Windows 10 without loosing the base partitions used for the "factory restore".  Thank you.
Clean install Windows 10