SOLVED: How To Do A Clean Install of Windows 10 Without a Product Key

Dec 2015 UPDATE: There ARE two ways to do a bare metal Windows 10 install from a machine with a Windows 7 or 8 licence:

1. PREVIOUS INTALL: If you had previously installed the November 2015 update (called TH2, 1511 and 10586) to Windows 10 and activated the machine using any key (i.e. integrated into BIOS or standalone key), you will be able to reinstall Windows 10 TH2 or newer without needing to enter the key because Microsoft’s Activation servers will remember your machine.   To be clear, if your hard drive fails and your Win 10 PC had been previously activated, it will automatically reactivate after you install a new disk and a fresh Win10 TH2 or newer.
2. FRESH INSTALL: If you have not installed Windows 10 on the PC previously and you want to do a bare metal install, you can do so by downloading Windows 10 using the most current Windows 10 Media Creation Tool (and yes there are different versions of that tool).  After you have installed Windows 10 November 2015 update, TH2 or newer, your PC should activate using your Windows 7 or Windows 8 key.  I have now done this more than 50 times on various types of hardware and found that 80% of the time big brand machines like Dell that have the Windows 8 product key embedded in the BIOS will activate as soon as the machine has booted and run its first patch cycle.  However 20% of those machines will not automatically activate and I have to use a simple and free tool to extract the Windows 8 product key from the BIOS and then use the CHANGE KEY function in Windows 10 to enter that key.  In all but 1 case, this has worked and in the case that it failed, I simply imaged the PC again and it automatically activated.

AUG 29 2015  UPDATE: Please read the COMMENT below BEFORE trying this as we have found it does NOT work.  I am working with MS Partner Support right now to clarify this problem and develop a solution.

OCT 18, 2015  UPDATE:  The answer is that you can NOT do a clean install of Windows 10 without a product key.  After banging through this with Microsoft Partner Support over the last two months the official response is that if you wipe your old machine (i.e. hard drive fails…) and you want to get Windows 10 without a Key, you MUST reinstall Win8.1 and then upgrade to Windows 10 (most likely using the disks you made using the Windows 10 Media Creation Tool outlined in the original post below).

…For the Windows 10 activation on the OEM machines, you need to first upgrade the Windows 8.1 machine to Windows 10, then Microsoft Activation Service will record the machine’s activation’s status and license(not the key) information. At this time, once you reinstall the machine with Windows 10, you don’t need to provide the key (you can skip the product key step) during the installation, the new Windows 10 on the machine will be activated automatically by the Microsoft Activation Service.  This is descripted in the following article: http://windows.microsoft.com/en-us/windows-10/activation-in-windows-10

…you need to do the upgrade first to get the Windows 10 Digital entitlement. Once you get the digital entitlement, you can reinstall the Windows 10 anytime, and it will be activated…

If you are a Microsoft Partner, you can read the entire thread which provides more detail HERE.  Thank you to “Green” for digging into this problem.

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The short answer is YES you can do a clean install of Windows 10 for free, but only after doing the upgrade from a previous version of Windows:

Once you’ve upgraded to Windows 10 using the free upgrade offer, you will be able to reinstall, including a clean install, on the same device. You won’t need a product key for re-activations on the same hardware… You’ll also be able to create your own installation media like a USB drive or DVD, and use that to upgrade your device or reinstall after you’ve upgraded.

So if your hard drive dies after you are running Windows 10 you can reinstall without a key and without paying as long as you have made the backup using the Win10 Media Creation Tool.

If you want the Windows 10 Media Creation Tool make sure you get the updated version see how to get the current version of the Windows 10 Media Creation Tool.