Can anyone help me with the steps for a clean perma Win10 installation? One method is to upgrade over a Daz or KMS activated Win7 / 8. I want a clean install of Win10 but using the license of Win7 or 8. So install Win 8.1, activate with KMS. Make the USB through MS Content Creator for Win10 Restart to Win10 installation. Setup asks for product key, select "I don't not have product key" Select upgrade or custom? Please help me at step 5, if I select upgrade, its going to keep the Win8.1 files and not be clean right? If I select custom, should I format? If I select the same partition, wont it be the same as upgrading? This step is usually not detailed in success story posts.