Method 1: Clean Install Windows 10
Instead of having to install Windows 7 first before installing Windows 10, you can cleanly install Windows 10 via downloaded ISO image and USB flash drive from Microsoft and enter old Windows 7 license or product key to activate new Windows 10 computer or laptop.
Method 2: Upgrade Windows 7 To Windows 10
Right-click downloaded Windows 10 ISO image and open with “Windows Explorer”;
Next, run the “setup” application to start upgrading Windows 7 to Windows 10;
When done upgrading, it gets a new digital license for your Windows 10 machine. However, before starting all this process, make sure your Windows 7 machine is activated via a genuine yet old Windows 7 product key.