If you’ve a genuine Windows 7 or 8.1 system, you’ve to upgrade to Windows 10 first (after that you can perform any number of clean installs you want), Microsoft uses ‘digital entitlement’, which doesn’t require your product keys to activate your Windows 10 copy.
Upgraded users have faced issues with Windows 10 activation, generally, your copy will be automatically activated when you’re online, but that’s not the case with all when Microsoft servers are busy, then troubled users have to contact Microsoft support to activate their copy.
Windows insider program head addresses Windows 10 activation issues
Gabe has acknowledged that and said while announcing Windows 10 preview build 10565 “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.”
Activate Windows 10 using Windows 7/8/8.1 Key
Now from Windows 10 insider build 10565 onwards or when it goes to public or available for Windows 10 RTM build 10240 users, they can use Windows 7 or Windows 8 or Windows 8,1 key to activate Windows 10 if they face any activation issues.
“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. ” he added.
To do that, visit Settings > Activation > Change product key, and enter product key of previous Windows version you’ve installed on your computer.
“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. Refer to the Insider Hub for more information on these activation improvements including requirements.”
Similarly, if you perform clean install of Windows 10 using Media Creation tool, then also without skipping the key entering part, they can insert previous Windows key (during the setup when asked), and after install, Windows 10 will be activated automatically.
Note : Here you should be using the same edition key. For instance, to activate Windows 10 Pro you should be using Windows 7 Pro key.
For Windows 8 or Windows 8.1 OEM, where the device key is embedded in the in BIOS, Windows 10 build 10565+ automatically uses the OEM key upon restart after the installation.
BTW, main news to insiders is : Microsoft has released Windows 10 build 10565 to insiders in the fast ring and is available to download via Windows Update. The build 10565 comes with new features, improvements and bug fixes.