This is how to change the Security settings on Domain Controller to windows 2008
Click Start, click Run, type gpmc.msc, and then click OK.
In the console tree, right-click Default Domain Controllers Policy in DomainsCurrent Domain NameDefault Domain Controllers Policy
In the Group Policy Management Editor window, in the console tree, go to Computer Policies/Windows Settings/Security Settings
To apply the Group Policy change immediately, either restart the domain controller or open a command prompt, type the following command, and then press ENTER: