Change Password Complexity Setting in Local Group Policy

The Password complexity is a Local Policy setting named "Passwords must meet complexity requirements" under Computer Configuration/Windows Settings/Security Settings/Account Policies/Password Policy.

In a Server Core installation there is no graphical user interface to set this policy.
Instead use secedit to import and export the security settings from a Full Installation of Windows Server 2008.

1. First export your security configuration using the following command:
   
   secedit /export /cfg C:\securityconfig.cfg
     
2. Then open notepad.exe and edit the C:\securityconfig.cfg file.
   Under [System Access] you should find PAssword complexity = 1
   Change the value to 0 and save the file.
    
3. Then fire up the next command to import the configuration:
   
   secedit /configure /db C:\Windows\security\new.sdb /cfg C:\securityconfig.cfg /areas SECURITYPOLICY