I have a 2 DCs (Main and Backup) both Windows 2003 R2 SP2. Both DNS and Both DHCP server (different Scopes). I would like to have these two serve as a time server in the domain and have all XP Pro clients sync their clocks with these domains. I would like these domain to get their clock from an external source (atomic clock) somewhere. How would I go about doing that? Anything to change in the group policy?