In practice Windows 7 and Windows 8.x keys still act as Windows 10 keys. All the activation mechanisms have been retested on the 18/10/2017 using Windows 10 RS3 Version 1709 (Build 16299).

The Free Upgrade – 1 Year Marketing

Windows 10 was released on the 29th of July 2015. Microsoft made it known that Windows 10 would be a Free Upgrade for those who took advantage of the Free Upgrade within the first year of release.

Theoretically the Free Upgrade should have ended on the 29th of July 2016 which has long passed.

In practice Windows 7 and Windows 8.x keys still act as Windows 10 keys. All the activation mechanisms have been tested on the 18/10/2017 using Windows 10 RS3 Version 1709 (Build 16299).

Why Product Activation Should Still Work After 1 Year

The initial release of Windows 10 build 10240 was however Upgrade only. This Activation Mechanism as I highlighted in the Windows Insider Program caused a lot of unnecessary grievances.  Following my advice (and the advice of numerous others) Microsoft made Windows 7 and Windows 8.x keys compatible with Windows 10 build 10586 installation media.

Windows 10 RS2 Installation Media is multi-Edition and should automatically input the SLP key from the MSDM for all the following OEM licenses:

Windows 10 RS2 will ask for a Product Key and accept the Windows 7 OEM key on the COA when it is manually input:

While Microsoft continued to heavily market the 1 year free upgrade deadline in a move to entice as many people to upgrade as soon as possible I suspected that Windows 7 and Windows 8.x keys were so embedded as part of Windows 10's installation and activation mechanisms that the free upgrade would continue indefinitely.

Microsoft could end the free upgrade by either patching the Windows Installation Media so it rejects Windows 7 OEM keys and Windows 8.x OEM keys however this would likely lead to a rise in the number of technical support calls as end users install the wrong Edition of Windows 10 and have to call Microsoft for support (opposed to just inputting their Windows 7 OEM key manually or inputting the Windows 8.x OEM key automatically).

Microsoft could also end the free upgrade by patching their Microsoft Product Activation servers like they did with build 10130. This however would elevate the number of calls for help with Microsoft Product Activation support unnecessarily. Moreover Microsoft want to migrate the entire Windows 7 and Windows 8.x userbase over to Windows 10 so they have only 1 Windows version to support and so their Windows store and Edge browser have the biggest userbase possible (with a continuous stream of revenue via advertising or Store purchases).

The Test Windows 10 Build 15063, Version 1703, RS2, Creator's Update with an Unused Windows 7 OEM COA

To test I need a system that has never had Windows 10 installed on and activated before. For demonstration purchases a system with a Windows 7 COA is better as Windows 10 can be installed without a Product Key and will not be activated if the system has never been made a Windows 10 Edition Device before.

I have bought several OptiPlex 790's to test this on. Here is the COA of one with the image modified to fade the first few characters faded to prevent piracy:

During Windows 10 RS2 Installation I can select "I don't have a Product Key" to install Windows 10 without a Product Key:

Because the COA is for Windows 7 Pro I should install Windows 10 Pro:

Once Windows is installed I can press [Windows] and [ r ] and type in winver:

You can see this is Build 15063, Version 1703:

I can press [Windows] and [ r ] and type in msinfo32:

Again you can see this is Build 15063, Version 1703 and I have installed Windows 10 Pro on the OptiPlex 790:  

If I right click the start button and select settings:

We can now see Windows is not activated. This is because Windows 10 is installed on a new system without a Product Key being input:

If I select Update & Security:

I can go to Activation: 

Now I may select Change Product Key:

If I input the Windows 7 OEM key from the COA and then press Next:

We can see that the installation media has accepted the Windows 7 Pro OEM key:

If I now press Activate:

I get Windows has been Activated. So I have confirmed that the Product Activation Server still accepts Windows 7 OEM keys for the initial activation of a Windows 10 installation (and not just for subsequent reinstallation of Windows 10 on Windows 10 Devices):