Hi,
Have you checked User Accounts Setting?
1. Open Run, Type netplwiz, Press Enter.
2. In the User Accounts interface, identify whether the option "Users must enter a user name and password to use this computer" was unchecked.
In addition, you may couldn't find this option, if so, you can change it directly in the registry by changing some values in the registry at:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
Set AutoAdminLogon to 0, Delete the
DefaultPassword value.
Note: the change of registry may be harmful with system, please make a backup before you make any change of it.
Roger Lu
TechNet Community Support
