Being your server is critical, I would advise you to setup a seperate Windows 2000 domain, clone your users from Winnt to Win2k using ADMT. Then you can use Active Directory connector to populate teh Ex5.5 directory info to ur AD. Then Install new E2K server joining the same site and org of 5.5. You may move mailboxes from 5.5 to e2k thereafter, followed by decommissioning the 5.5 server and finally switching to e2k native mode. Regards, Rajesh