E6530, broken after BIOS Update

Hello;

I bought few years ago E6530 (i7), used. Have to say that I already have new, other, Dell Laptop, for primary use.

During the BIOS update, I went with all requested steps, but, after that, Laptop was not responding at all.

I checked some of those steps for diagnosing, screen one was okay, but based on tests, it was the issue with BIOS.

Okay, I tried to use CH341A to flash the BIOS to two BIOS chips on Motherboard. Flash worked, but, with issues, problem was not resolved.

Next step was to replace BIOS chips, with new ones, with already flashed BIOS software on them. Unfortunately, during BIOS chips removal, the Motherboard contacts were broken.

After that, I bought few E6530's (decommissioned, for parts), but those were with i5 CPU. I used those (2 of them) for VMs (Labs).

Finally, I found and bought used Motherboard, the generation of the one at the E6530, which I am trying to fix.

So, everything prepared, step by step I replaced the old broken Motherboard with the used one, I put Arctic MX-4 thermal paste behind CPU and GPU cooler, assembled all parts, and, it started properly. All looks well, just one issue.

Issue is related to the Windows 10 Activation. Windows License is connected to the Motherboard. Replacing Motherboard Windows is considering as replacement of the Laptop itself, which is part of the problem.

I still have Service Tag number from the Laptop, and behind the battery, there's Windows 7 Pro OA Key.

New (used) Motherboard has different Service Tag visible when BIOS is viewed.

I tried to Activate the Windows, using the Key from the Laptop, it does not work (I tried it using the same SSD drive inside, which was used at the Laptop before it's BIOS was broken).

Now, I have to say that I already spent a lots of time, significant amount of money and at the end, Hardware issue was solved, but OS issue was not. By Microsoft logic, if user is changing the engine, motor at the car, there is a must to change license plates, maybe even more docs and stuff.

Really hope that there's a good, clear step by step process to do this, as the Windows I have is legal, legitimate. I saw some discussions here about this topic.

Any suggestions about best, fast, next steps to be done, to have the Windows Activation done properly?

Thanks a lot.