If so, I'll loose my free Win 10 installation as it is based on the board.
I think the best you can do is to replace the board with a current board, which means new processor, new memory, etc.
You might find a functional replacement on that auction site. Or, you might find a board that is being sold for parts.
I would not worry about a windows 10 license key. There seems to be a dozen or so ways to get to W10.
Now, my honest opinion - Get a replacement board. This is likely not the only failure you are going to have with a board this old. Yes, I know there is a cost involved. But, you will be replacing it in the near future for sure.