New
#11
As long as the machine recorded on the MS activation server has had no major change in its components - this usually means just the motherboard (even that COULD be approved by calling MS) - the Win10 activation is good for the life of the machine. This means you can do the clean install as many times as you need and, yes, repeat the upgrade process as many times as you like. In fact, repeating an "in-place" upgrade is a way to reverse any problematic changes you may have made to the Win10 install that you come to regret.
If you reinstall Win 8.1, then that would still have to be activated by it's own pre-existing method before you go on to a repeat upgrade of Win10 - in that case, I'm not aware of any reason MS would block Win10 activation, even though it may have recorded an identical machine ID in the past. Your Win 8.1 license has not been revoked and (up until July 2016) the free Win10 upgrade offer still stands.
After July 2016, I don't believe you can repeat the Win 8.1 install/activation and then upgrade to WIn10 without having to buy a license - what kind of deal MS will offer at that point, I haven't found any information on.
You might consider capturing images of the system with freshly installed and activated Win 8.1 and same for Win10 with a good 3rd party program like Macrium Reflect Free if you have external storage available. That can secure the installs and data for any back and forth you end up doing.
So can you again just confirm what I have to do now.
Do a factory reset to windows 8.1 and confirm that its activated. Upgrade normally. Confirm win 10 is activated. Then do a clean install from win 10 only.
Is there any method in which I dont have to download the 3 GB file again and somehow I can use the dvd to do the upgrade?