If you want or have tried to activate Windows 10 Pro from the ISO file with your previous license Windows 7 or Windows 8.1, you may have found that you are not able to activate your newly installed operating system. Do not worry, it’s normal. According to Microsoft, a valid license of Windows 7 or Windows 8.1 will not be able to activate Windows 10 because it uses its own product key and hence the error in activation.
A license of Windows 7 or Windows 8.1 gives you the right to upgrade to Windows 10 but not allow clean facilities at first and therefore the solution is to first migrate to Windows via update.
Once you’ve upgraded to Windows 10 and the system is automatically activated, the activation server products Microsoft will register the equipment in question and considered as a certified Windows 10 computer. Official Windows 10 Disc Image (ISO) here.
From there , you can create a bootable ISO DVD or USB and make clean facilities you want. Microsoft server detects the computer and perform validation automatically.
All this refers to previous licenses of Windows 7 and Windows 8.1 not new retail copies of Windows 10 that Microsoft is selling itself and obviously can use to install from scratch on any computer.
We have put the tagline of “legit” solution because it is not unlikely that pirate activation methods will continue to work. In fact, some users have been able to upgrade to Windows 10 pirated copies of W7 or 8.1.
To conclude, if you have a computer with Windows 7 or 8.1 license have to make first upgrade to Windows 10, check this link out for a guide to help you. Then you can use the ISO and clean install from scratch.