I have 7 Windows 2000 DC:s (3 SP4 and 4 SP3) in my domain. Clustered (Act/Pas) Exchange 2003 on Windows 2000 Adv Srv (SP4). Planning to upgrade Exchange 2003 platform from Win2000 Adv Srv to Windows 2003 Ent Srv. Would it be smooth or hard ? Any experiences ..anybody..?