Yes I know this problem!
I can solve it! (but on Linux
It gives this error because you cannot
create users if you haven't got admin's premissions!
You can hack the password if you want with C++. I will do a video how to do it (Working on Windows 7, XP, Vista, 8, 2000 and more!). Then you can create a Admin Type user.
Admin -> Admin type
User -> User type
Guest -> User type, No password
Admin -> Users / Guests
User -> nothing
Guest -> nothing
I'd ;ike I was helpful!