One suggestion give was to back up the data files. If you can do that logged in with Admin rights I've had success in creating a new User with Local Account with Admin rights, reboot and choose that new user and delete the old user. Unless there's something the Microsoft Account had that is needed there should be no issue with using the computer. Also, is it possible the initial setup used an E-Mail address for the MS Account and also the same password for it? Maybe that is available.