Take a look at this KB artical as it demonstrates how to add domain administrators group to local administrators. This will work for you all you need to do is change the domain administrators group to domain users and it should work.
http://support.microsoft.com/kb/555026Also here is a link to create a GPO...
http://www.windowsecurity.com/articles/Group-Policy-related-changes-Windows-Server-2008-Part1.htmlhttp://trycatch.be/blogs/roggenk/archive/2007/07/25/windows-server-2008-amp-group-policy-management-console-gpmc.aspxHope this helps~!