De link
To lift the password complexity:
secedit /export /cfg C:\new.cfg
Then you edit new.cfg (it is ini format) and change line “PasswordComplexity = 1″ to “PasswordComplexity = 0″.
Apply it with:
secedit /configure /db %windir%\security\new.sdb /cfg C:\new.cfg /areas SECURITYPOLICY