I had a look at my GOG.com FS2, and you may be able to get fix on GOG FS2 installations using the following registry key:
I'm not sure where GOG stores its install paths (I checked Program Files (x86)\GOG.com\ and didn't find anything).
EDIT: OK, found it, it's in
- not sure what the file storage spec is, but you can read FS2's install path in plain text.
EDIT2: The above is probably more reliable as the user might have changed the install location, but you can also find the normal GOG Library location in plain text from
EDIT3: of course that all relies on having Galaxy installed instead of using the stand-alone installer. The registry key I initially pointed out would be better in that case then? I dunno what's best, neither, both, or one then the other. If you need more tests / searches done, let me know and I can help.