Mike here. Windows Vista made numerous changes with how user profiles work. In fact, the changes are too numerous to describe here (you can read more about the changes with user profiles in the Managing Roaming User Data Deployment Guide (http://go.microsoft.com/fwlink/?LinkId=73435). However, the policy settings for user profiles from earlier versions of Windows remain and Windows Vista introduces five new policy settings.
Four of the five new policy settings for user profiles exist under Computer Configuration\Administrative Templates\System\User Profiles (the remaining policy setting uses the same path under User Configuration). These five policy settings apply only to computers running Windows Server 2008 or Windows Vista, however; these policy settings can co-exist in GPO’s applicable to clients earlier than Windows Vista. Operating systems other than Windows Vista ignore the policy settings. Let me begin with the policy settings under the computer configuration and then close with the single user setting.
Full Article – http://blogs.technet.com/askds/archive/2008/06/17/user-profile-policies-in-windows-server-2008-and-windows-vista.aspx