Here's what I learned from my Win 7 Pro upgrade to Windows 10.
I have 2 OEM activate Windows 7 PC's.
Both showed the Windows 10 upgrade icon and I reserved my copy, but neither machines showed the update as available in Windows Update..
I tried the below and add the reg key to the registry and the upgrade showed in Windows update...all 2.7 GB of it.
https://www.reddit.com/r/techsuppor...t_install_windows_10_have_tried_wuauclt_have/
Both machines downloaded the update and installed and upgraded to Win10 no issues.
I made sure both were activated.
I Decided to do a RESET on the machine I had now upgraded, this worked perfectly. Clean Windows and it was activated.Yay.
Then on the same machine I decide to do a complete wipe and install from the ISO image I had download from MS via the update tool.
During the install I choose to skip entering a Product key (as Win 7/8 key will not work anyway).
Once the install was done and everything was up and running, Windows 10 would not activate and told me that the product key was blocked. I was rather stumped.....and annoyed.
Some furious investigation and I found + noticed the following....
: When installing from scratch using the x64 ISO(or bootable image of the ISO), for some reason Win 10 Home had installed?? (I dont remember seeing an option to choose?), not Pro. This is something to keep in mind if you've also gone for the full reinstall.
Since my machine was licensed for Win 10 Pro, it would not activate on Win 10 Home.
Using details found here:
http://www.ghacks.net/2015/07/29/how-to-do-a-clean-install-of-windows-10/ I noticed that the product key my machine was showing was the HOME product key.
I choose to upgrade/change my Product key and used the "Pro" product and viola! Windows 10 told me it was upgrading features!! Once done I rebooted and Windows 10 was upgraded from Home to Pro and showed as ACTIVATED.
Since then everything is working as it should.