After Greetings.... I Have a Exchange Server 5.5 With SP4 running on top of Windows NT 4.0 (SP 6) Box. i want to install exchange 2000 on another server which path i have to follow.Currnet Setup is Windows 2000 Domain controller machine with Active Directory running on it. This is a seprate machine, with Win2k SP2. The steps whihc i am trying is installation of exchange 2000 server on seprate windows 2000 machine. before installing exchange 2000 i have used /forestprep and /domainprep on domain controller. After installing exchange 2000 i tried installing and configuring Active directory connector, which i was unable to as exchange 2000 is unable to communicate with exchange 5.5 computer. My goal in this scenario is to use exchange 5.5 GAL and communication between two servers. Slowly i will move my all users to exchange 2000 and remove exchange 5.5 from the network. In this case i'll not have any downtime and if anything goes wrong istill have my 5.5 up and running. So if anybody had done this before of if anybody can suggest anything good for migration from 5.5 to 2000 with less down time. please help me. Vijay Dogra.