A retail version of Windows 7 Pro might be transferable to a new motherboard. An OEM version is not. you can prove it was a retail version, you have a stronger case.
My MB fried last month and I replaced it a couple of days ago. Windows 10 Pro is now deactivated. I did all the steps online and used the troubleshooter repeatedly to no avail. Online chat was useless as they wanted me to dig up a receipt for my OS from years ago as this was an upgrade from 7 Pro.
Based on feedback here and elsewhere I have called them but the person who I talked to said my MB owned the OS, not me. Because the MB died I need to pony up another $200 even though my system and 5 others I own are recognized on my Microsoft account as being good to go a month ago.
Has anyone else dealt with this nonsense recently? My MB did not waltz down to the store and buy the OS. I bought it. A hardware failure should not require me to buy another OS that was fine 30 days ago. Their insistence that I show a receipt from a decade ago for Windows 7 Pro is ludicrous.
The fact the system is recognized on my Microsoft account should be enough. Now it sees two systems with the same name but neither has an official OS all because of a MB change. I have 5 systems and and each one has a real OS not to mention the serious coin spent on MS Office!
I was told to call back in an hour if I want to talk to a supervisor and in 20 minutes I will do just that. I am always polite but can see how someone could be easily frustrated with the experience. I will post back with the results from my conversation with the supervisor in a bit.