Cannot Access Accounts Other Then The Built-in Administrator

I've enabled the built-in Administrator account. However, I can no longer access my other account (which is also an Admin account). I even tried creating another account, which also cannot be accessed.Basically: upon login, I get the login screen, however there's only one account, which is the Administrator account. There is a 'switch user' button, which just shows the 'Other Users', which doesn't do anything: entering any account details only says 'invalid username or password'.The first account was created BEFORE I enabled the admin account; the user folder is still there. However, the new account I created has no user folder.