I originally had setup /PrepareAD fail on me with object referencing a null object. See post: http://forums.microsoft.com/TechNet/ShowPost.aspx?PostID=3562261&SiteID=17&mode=1 We originally had exchange 2000 installed on Server 1, and did a coexistence upgrade to 2007 on Server 2. Due to problems with the initial implementation of exchange 2007, we then downgraded to a coexistence Ex2003 on Server 1 and uninstalled 2007. A new server specifically for exchange 2007 has been added as Server 3. This is a fresh install of Server 2003 R2 x64 with all available updates, and all preqreqs for Exchange 2007 SP1have been met. During the setup of 2007 SP1, the client access role fails but all other roles are successful. Client Access Role fails GUI setup Summary:1 item(s). 0 succeeded, 1 failed. Elapsed time: 00:00:13 Client Access RoleFailed Error:Exchange server "mydomain.com/Configuration/Deleted Objects/ServersDEL:58d2240c-c282-4726-a06b-bdce44be2bdb/TR-SRV3EDEL:09e2fbb8-893a-411d-ba42-a5ac2c9e1bfb" was not found. Please make sure you have typed it correctly. Elapsed Time: 00:00:13 I've used LDP and viewed the deleted objects container and active directory explorer by sysinternals and I cannot find this GUID or any reference to the old server. I have also changed the tombstone lifetime to 1. I'm not sure if this will forcibly default to 2 days since it seems 2 days is the minimum. And i've done an offline defragmentation of my AD and forced push replication out from that domain controller to no avail. I can only assume the tombstone objects still exist in AD from my decommissioned exchange 2007 server. How do i manually remove old tombstones?

Problem Solved. An oversight on my part of downgrading from exchange 2007 originally led to this. The offline address book was still pointing to the old server. I created a new OAB, set it as default, updated it, then removed the old OAB. Client access role installs fine. Goodluck everyone.