I do have a quick question for you though: I was wondering what each of the 3 main registry entries do.
MPAccountName and MPAccountNameSig seem to be the items that your AM stores, but I'm not sure about the InstallKey itself. The reason I ask is that I created a multiplayer account on a temporary user on this computer, saved all that user's data in the AccountManager, and can access the account from my main user; works as expected. The weird thing is if I change the InstallKey value to something else (like the account ID my lady uses) I can still get to my account data -- is this supposed to happen? It almost seems like the InstallKey value doesn't change anything on my PC -- I can still get to the same accounts no matter which InstallKey I use.