Unbelievably I know, we're still on 5.5. I plan to build a new 2007 server from scratch. In a test environment ( a functioning copy of our current domain but without the 5.5 server), I'm starting the AD prep using an Exchange 2007 Std W/SP1 DVD media. The "setup /prepareschema" command worked fine but the "setup /PrepareAD /OrganizationName:MyDomainName" failed with the message:Organization Preparation ......................... FAILED Active Directory operation failed on DC01.Lobel.Local. This error is not retriable. Additional information: An attempt was made to modify an object to include an attribute that is not legal for its class.Active directory response: 0000207D: UpdErr: DSID-031514DE, problem 6002 (OBJ_CLASS_VIOLATION), data -1641360258There are two other things. I had installed ADC on 5.5 long ago and it got broken when I decommissioned the old PDC years ago. Also, we have Nortel unified messaging connected to the exchange server somehow. Either one of those may be causing it? I don't know what to do besides calling in an incident.Any help?

Check the exchange set up log and paste the line which has got errors on it. Also check if the post helps you http://social.technet.microsoft.com/Forums/en/exchangesvrdeploy/thread/1f432502-9aaf-439a-8cb8-101b38efb695Raj

Raj:Thanks for your response. I didn't notice it til I came back her just now to post the fix that I had to pay MS for. They had me do the following, which worked. On the domain controller, with the exchange DVD in the drive, run a cmd prompt as Administrator. Then:Change to the DVD-ROM drive letter and issue the command: setup.com /ps You should get a message that it was successful. Issue the command: setup /P /on:YourOrgName Mine failed on the command above. Issue the command a second time: setup.com /ps You should get a message that it was successful. Issue the command: setup /P It was successful.