Try setting the passwords to blank or empty entries. Keep in mind that I too see some inconsistencies in the user management area of Windows 8. I'm not writing it's right but that there is a problem in this area.
Managing your account appears in the full metro interface, creating a new user or dealing with another user uses a "windowed" interface and let's be frank. This was rushed to market. It may take a few more years to get fixed.
Bob
After I installed updates today my Dell Latitude 10 Windows 8 tablet and restarted it started to require a password on start up. I went to "run" and typed in "netplwiz" and got to the "User Accounts" window. The problem is that there is no "Users must enter a user name and password to use this computer" check box. Is there another way to remove the password from start up?

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