This ended up being fairly twisted and I imagine had to do with mis-set registry values. Somehow when I upgraded from MySQL 5.1 to 5.5 last November it moved the three main big files, but it never moved all the .frm directories. Those are all still in the documents-and-settings area, in the 5.1 subdirectory.
So what I did was, over on my other Windows 2003 server, I made a fresh install of MySQL 5.5.15 so it matched. Then I moved over the three innodb files into the documents-and-settings data directory. I then separately moved all the .frm directories in, which came from the 5.1 subdirectory. I gave them the my.ini file from the main program files directory. I ran it from the command prompt - and I could see the databases! I promptly dumped them all out to text files.
On the new server, I'm making a fresh, clean install of 5.5.15 again to keep everything as simple as possible. Then I'll import those dump files. And back everything up.
Only then will I think about upgrading
.
So right now I'm at the stage of moving those dump files onto the new server, and giving it a fresh, clean version of 5.5.15.
