So it’s a good idea to backup everything using the right backup solution. Step 2: On your Windows 10 PC, where you want to perform a clean install of Windows 10, back up all data as we are going to clean install Windows 10 by removing installed programs and personal files. Step 1: If you haven’t downloaded your Windows 10 ISO yet, please follow the instructions in our download Windows 10 ISO from Microsoft guide to download the ISO image file. Here is how to clean install Windows 10 from the ISO image file without having to create a bootable USB or DVD. Perform a clean install of Windows 10 from ISO image If at all, Windows 10 is not activated after the clean install or reinstall, use the built-in activation troubleshooter to fix the issue. However, when you clean install Windows 10 on a different PC or newly built PC, you will have to enter a valid product key. Your PC will be automatically activated after installing Windows 10 as long as you have installed the same edition of Windows 10 was activated on your current PC by using the free upgrade offer. When you are prompted to enter a product key during the product installation, click the Skip button.