Clean installing Windows 10 can be a pain. There's too many gotchas that it can be frustrating.
Here's how I did it:
- -download the MEDIA CREATION TOOL for WINDOWS 10.
- -after your have created the USB, check to make sure you have the right BUILD NUMBER (see other article post).
- -SKIP PRODUCT KEY DURING INSTALL (OR "Do This Later or I Don't Have a Key"). Save the activation after install with your Windows 7, 8 or 8.1 Product Key, even if embedded in BIOS.
(NOTE: this is in contrast to the WINDOWS 8 that requires to NOT select "I don't have a product key" as activation will not be successful. )