Windows 10 comes as a free upgrade for those on Windows 7 and 8.1, and in order to get a copy of the new operating system activated, users need to first perform the direct upgrade and wait for it to be automatically validated by Microsoft servers.
Once this happens, Windows 10 adopters can easily perform a clean install because the product key is bound to the used Microsoft account and existing hardware configuration.
But it's not a secret that, for many, this new system failed to work correctly and lots of Windows 10 upgraders actually had to wait several days to get their copy of the OS activated either because Microsoft's servers were overwhelmed due to the number of computers attempting to connect or because the fact that something went wrong on users' PCs.
With Windows 10 Insider Preview builds, Microsoft has been experimenting with a new system that makes the activation process a lot simpler, as it allows product keys that came with Windows 7 or 8.1 to be used for the new OS.
The first time the company implemented this change was in Windows 10 build 10565, and the Threshold 2 update coming in early November will also bring this change to stable users.
“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,” Gabe Aul, head of the Windows Insider program, explained how the new system worked in build 10565.
Given the fact that Threshold 2 will be the new default (users upgrading from Windows 7 or 8.1 to Windows 10 will get directly to Threshold 2, just like those resetting their PCs), such a change really comes in handy and is supposed to fix any trouble you might have with the activation system.
Microsoft hasn't yet confirmed this new system for RTM users, so take it as a rumor until a confirmation is being offered.