Threshold 2, the first big official upgrade to Windows 10 since its July 29 launch, is on schedule for arrival next month. Members of the Windows Insider program have been testing previews of the new builds for the past month, and the latest Threshold 2 preview release, build 10565, contains a welcome change.
Effective with this new build, you can do a clean install of Windows 10 using a product key for a corresponding edition of Windows 7, Windows 8, or Windows 8.1 on that device. (Update 14-Oct: I've now done enough testing to confirm that any key from a previous version that's eligible for the upgrade will work with a clean install of Windows 10, at least on this build. See details at the end of this post, and note that this feature is still limited to Insider preview builds and is not yet available for the released version of Windows 10.)
Some background: For the initial release of Windows 10, Microsoft radically revised its activation rules, effectively eliminating the role of product keys in most upgrades. (For details, see "Microsoft quietly rewrites its activation rules for Windows 10.")
The current rules, in place for the July 29 public release, make it easier to reinstall Windows 10 on a PC that's already been activated. That's because Microsoft's activation servers can recognize your PC, based on its hardware fingerprint, match it with the saved activation record, and automatically approve the activation request online.
But those same rules cause headaches for Windows purists who prefer to start with a squeaky clean install when moving to a new operating system. In the initial public release (build 10240), Windows 10 required at least one upgrade install over a fully activated Windows 7 or Windows 8.1 PC to enroll the PC's Windows 10 license on Redmond's activation servers. After that enrollment is successful, those servers are able to activate the PC automatically when the proper edition of Windows 10 is installed later, assuming the hardware hasn't been significantly changed.
If you skip that initial upgrade step, as many Windows experts choose to do, you have to supply a Windows 10 product key to activate. Because the one-year free upgrade offer doesn't include a product key as part of the package, you're stuck in limbo, unactivated. Your only option is to restore and activate Windows 7 or 8.1, then upgrade to Windows 10, or buy a new product key.
The product key changes coming in Threshold 2 offer a third alternative. Here's the official announcement:
We have received a lot of feedback from Insiders on making it easier to activate Windows 10 on devices that take advantage of the free upgrade offer to genuine Windows by using existing Windows 7, Windows 8 or Windows 8.1 product keys. If you install this build of the Windows 10 Insider Preview on a PC and it doesn't automatically activate, you can enter the product key from Windows 7, Windows 8 or Windows 8.1 used to activate the prior Windows version on the same device to activate Windows 10 by going to Settings > Update & security > Activation and selecting Change Product Key. If you do a clean install of Windows 10 by booting off the media, you can also enter the product key from prior Windows versions on qualifying devices during setup.
After some testing, I can confirm this feature works as advertised.
Using a freshly created virtual machine, I installed Windows 8.1 Pro using a valid product key, after completing the installation I confirmed that it was properly activated.
Next, I rebooted the system using Windows 10 installation media. One ISO file was created using the Microsoft Media Creator Tool; it contained build 10240. I created the second ISO using a successful Windows Insider upgrade to build 10565. (For details, see "How to turn your Windows 10 upgrade files into an ISO disk image.")
During Setup, the Windows 10 installer prompts for a product key. When I used the Windows 10 build 10240 media, this step would accept only a Windows 10 key. Entering the Windows 8.1 Pro key I had used previously on this virtual machine resulted in the error message shown at the top of this page.
This behavior was very different when I booted using the installation media for build 10565. Here, I was able to enter my Windows 8.1 Pro key, which was accepted by Windows 10 setup and allowed me to continue. After completing the installation, I confirmed that the new Windows 10 build was properly activated.
I repeated this experiment using a clean new virtual machine with Windows 7 Pro installed. After confirming that Windows 7 was properly activated, I booted using Windows 10 (build 10565) installation media, wiped and reformatted the disk, and then did a clean install. The Windows 10 Setup program accepted the Windows 7 product key, and within an hour after the clean install was complete, Windows 10 was activated.
You can click the Skip button during Setup, allowing you to continue installation without a product key.
After the clean install is complete and you're connected to the Internet, you are given another opportunity to enter the product key.
You can also skip this step, using the Do This Later link in the lower left. If you do that, you need to enter the key later, using the Activation page in Settings. Until you do that, some features of Windows 10 won't work properly.
If this feature works as expected, this means you will have three opportunities to supply the Windows 7 or Windows 8.1 product key that was used to activate that earlier version on the current hardware. If the key matches, your PC is given a "digital entitlement" via the Windows 10 activation servers and you are officially on easy street.
This feature is going to require a fair amount of tedious testing. I assumed, for example, based on the language in Microsoft's announcement, that the activation servers would insist on a match between the product key you enter and the existing activation record. That would prevent someone from "recycling" old product keys for mass installations.
However, my initial testing turned up different results. I did a clean install of Windows 10 Pro on a virtual machine with Windows 7 Ultimate installed, wiping the disk in the process. After setup was complete, I entered a completely different Windows 7 Ultimate product key than the one initially used to activate that OS on that PC. Windows 10 accepted the never-before-used product key and activated the clean install of Windows 10.
And in an additional test, I did a completely clean installation of Windows 10 Pro build 10565 on a virtual machine that had never seen any other OS. As expected, it was not activated after the installation was complete. But I was able to complete activation in a matter of seconds by entering a previously unused product key for Windows 8 Pro
For now, preview builds are delivered only through the opt-in Insider channel in Windows Update. They aren't yet available for download as ISO files that can be installed independently, which limits testing opportunities.
If you're an Insider working with the new build, I'm interested in hearing your comments. Leave them here or use the contact form in my bio to send an email.