Server 2008 password problem

[New]

I have installed Server 2008.After the installation is complete it asks to give a password(like vista,but here you must give).If I enter the password it gives an error like this"Unable to update the password.The value provided for the new password does not meet the length, complexity or history requirements of the domain..
Please tell me how to give password..Is there any specific way for win server 2008?
Thanks in advance..

[techtronic]

Password complexity in Windows Server 2003 specifies 1 number and 1 special character to be included in your password.Guess it has to be the same in Windows Server 2008.