Hi All,Here's my setup;dc-1 - Windows 2003 Standard - Domain Controller, Has all 5 operations masters and is a global catalog and DNS server alsodc-2 - Windows 2003 Standard - Domain Controller, also is a GC and runs AD Integrated DNSapps-1 - Windows 2003 64x Standard member server - This is the target for the Exchange server. This installation of 2007 would be the the first Exchange server in the domainDomain is running in 2003 Native ModeForest is running in 2003 Native modeI've ran the /schemaprep and that went through fine. I'm now running to run /adprep and am getting;Organization Preparation ......................... FAILED The directory service is unable to create the Universal Security Group Exchange Servers in the domain OU=Microsoft Exchange Security Groups,DC=uks,DC=local. Please verify that the domain is in Windows 2000 Native Mode. I've googled this as much as I can and can't find a single fault. DCDiag reports clean against both domain controllers. Googling does say try removing Exchange via ADSI Edit, done that and it failed with the same error. One other google suggested removing and recreatign the admin profile, I've tried that and it failed.Any input from anyone on this would be greatly appreciated.ThanksGavin

Hi, Have you tried to create the universal group "Exchange Servers" manually to see what happens? Leif

I've just tried that and I'm now getting;'Windows cannot create the object 'Exchange servers' because: The specified group type is invalid'I've checked in Active Directory Domains and trusts and both my Domain Functional Level and my Forest Functional Level are set to Windows Server 2003. What would be causing this? From the reading I've done this is only seen if you're running in mixed mode?ThanksGavin

Right. I've now solved this.One of the DC's of my pair was reporting a 'Schema mismatch' between itself and the schema master. I've migrated the schema from the schema master to the other domain controller. Re-ran /adprep and it went through sucessfully. I'm going to demote and rebuild the faulting domain controller to see if that rectifies the fault.As it stands I have Exchange 2007 installing on the other screen Command I used was ; "setup /adprep /domaincontrollerc-1 /organizationname:myorg"Does anyone know if this forum is indexed by google as this problem was incredibly elusive to track down and it would be nice to know this helps someone else.ThanksGavin