My Windows 10 PC was never set up to need a password and suddenly it's wanting one. It would not accept my password so I changed it. The next time I try to log in, my new password doesn't work. It will only accept one of 4 old passwords. It changes which password it will accept each time I try to log in. Thank you.

The next time you come in, just disable this feature and that's it!

I don't use Win 10 but in Win 7 if you open the run box and type CONTROL USERPASSWORDS2 there is a box to uncheck for not needing to enter a password at boot up. If there is a check in the box, it activates the change password feature. If it's unchecked the change passwords feature is greyed out.