Hi
You probably got the information you need from Neemo.
But I've found that the easiest way to deal with Microsoft Account issues is to log into your account on the net.
Sign in to your Microsoft account
Your account it tied to the email address you used to create it, as long as you know that you shouldn't have any problems, and if you don't know what your password is there is a process to recover it, or create a new one.
Once you have an account set up with a password and can log into your account online, you should be able to log into your computer using that email address and password.
Your old information was stored on your mother board, so when you changed it, the login info went with it.
Mike