Microsoft has been giving away Windows 10 for free to Windows 7 and Windows 8 users since launch.
However, those free upgrade offers come with a catch: you can’t perform a clean Windows 10 install. You need to install the Windows 10 upgrade.
Fortunately, there is a way to perform a clean Windows 10 install for free. The new Windows 10 update actually made it easier. Here’s our guide:
Step 1) Perform a Clean Install of Windows 10 by downloading Windows 10 here
Step 2) Update Windows 10 to the latest version
Step 3) Once you’re updated, search for Activate in Cortana
Step 4) Type in your Windows 7 or Windows 8/8.1 product key on the activation page to register Windows 10
Alternatively, you can reach the Activate menu by going to Settings > Update & Security > Activation > Change Product Key.

Or, you can also enter your Windows 7 or Windows 8/8.1 product key during the setup process when clean installing Windows 10 and that will perform the same activation.
Prior the new update, performing a clean install and upgrading for free was a weirdly lengthy process involving reformatting, installing Windows 7, and installing Windows 10 all over again. The new update makes it significantly easier to perform a clean install of your free version of Windows 10.