Two accounts at login startup

[btr999]

My build is 14393.1770 version 1607 Windows 10 Pro. My pc started up without password but starting yesterday, 2 same accounts appear on my login screen and I have to type in password to log in.
In netplwiz the "users must enter a user name and password" is already unchecked.
Control Panel - User account shows only 1 account aka administrator.

Is my pc infected? Any help please? thanks in advance

 

[SoggyTissue]

is the second account a 'guest' account? a guest account can be active (not logged in but shown) even with just 1 normal admin account.

did windows update before this change? sometimes an update my have a bug in it, activating the guest account. whats the extra account name? guest?

 

[btr999]

is the second account a 'guest' account? a guest account can be active (not logged in but shown) even with just 1 normal admin account.

did windows update before this change? sometimes an update my have a bug in it, activating the guest account. whats the extra account name? guest?

Both are the same account, administrator. Same id, same password. And as I mentioned, in the user account setting, there is only one account and it is the administrator account.
I am not sure if windows updated. I didn't really try to memorize every build and version. It happens about 1-2 days ago.
I have no way to remove the second account because it doesn't exist and in netplwiz, the require password option has already been unchecked but it still asks for password when starting up.

 

[SoggyTissue]

although i dont recommend this, you could try:

creating new admin account with a different name, deleting the first primary account afterwards. does this remove both original named admins?

else windows recovery to roll back/system restore.