Notice:
If your computer has ever had a valid, licensed copy of Windows 10 installed, even if that's been later replaced by, say, Linux, you can still do a completely clean install of Windows 10 without having to acquire a new license. Windows 10 licenses are stored electronically on Microsoft servers, and are linked to your computer's motherboard. The installer will locate that existing license if you are reinstalling Windows 10.
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I decided to update these instructions and make downloadable versions available so that those who want to use them can have a copy right next to them to refer to when using them. You can use the Windows 10 Media Creation Tool either to create bootable USB media directly, or if you want to have a copy of the ISO file, to download that and use a separate utility to create the bootable USB media. Either way will work.
It should go without saying, but I'll say it anyway, that if you have a functioning, even poorly functioning, system that you're hoping to wipe clean to get a fresh start that you should definitely do a full system image backup and a separate user data backup before following the instructions for doing a completely clean reinstallation. It also makes sense to use a utility such as Belarc Advisor to create an inventory of the software you have installed and the license keys for same so that you have a handy list when it comes time to put them on your brand, spankin' new Windows 10.
Edited by britechguy, 08 February 2019 - 03:16 PM.
Added Notice regarding Windows 10 licensing