Password must meet complexity requirements Computer Configuration\Windows Settings\Security Settings\Account Policies\Password Policy
Determines whether passwords must meet complexity requirements.
If this policy is enabled, passwords must meet the following minimum requirements:
Not contain all or part of the user's account name
Be at least six characters in length
Contain characters from three of the following four categories:
English uppercase characters (A through Z)
English lowercase characters (a through z)
Base 10 digits (0 through 9)
Nonalphanumeric characters (e.g., !, $, #, %)
Complexity requirements are enforced when passwords are changed or created.
To create custom password filters, see the Microsoft Platform Software Development Kit and the Microsoft Technet.