The FAM will only work with the MPAccountName and MPAccountNameSig values. The install key won't be touched.
As FL is closed source, I don't fully know how the game manages the three registry key. They are related somehow. I know that the sig is some kind of hash of the account name, and both must coincide. But how the installkey is related, i dont know.
Only the account code. The program will take the argument, look for it on the database, and take the sig from there. Don't forget that in order for it to work, the account must exist on the database first.
Windows Vista seems to handle the registry in a different way. Also, the installer must be modified to work with Vista. Once I "get" a copy of vista, I will test the program there, and fix the Vista issues.
(If you find any mistake in my English, please let me know via a PM)
(Really, I speak terrible English, so please, tell me if I make mistakes. I'd like to improve it a bit )