Need expert advice on corrupt Exchange 2010 transition, possible removal and reinstall

Setup:  I have an existing 2 server exchange organization (2003 SP2 FE & Mailbox).  I built/added 2 new Exchange 2010 SP1 servers (CAS/HT/Mailbox).  All proper prerequisites were followed, including all AD related prerequisites.  All went perfectly well.  These were clean installs and nothing was changed/done with the Ex2010 configuration, with the exception of creating a CAS Array.  After attempting to install Ex2010 SP2 on one of the servers, the upgrade failed and I now get a message when attempting to rerun the upgrade that the installation path is unavailable in the registry and that only disaster recovery mode is available.  Exchange 2010 does not show up in Add/Remove Programs.  The EMC or EM Shell will not launch.

As of now the Exchange 2003 environment continues to work normal and as far as I know the other Ex2010 server is still alright.  

I need an expert to tell me what I need to do to correct this issue.  Research is indicating that its going to take a clean reinstall of Server 2008 R2 and a reinstall of Exchange.  I need specific steps with details because of the integration of AD and the existing Ex2003 org that it was introduced into.  I do not want to mess up AD or the existing Ex2003 environment.  

Answers/Advice please?
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Madan SharmaConsultantCommented:
As Exchange 2010 SP2 makes updates to the Active Directory schema and client access server prerequisites are also change now its requires IIS 6 WMI Compatibility.

So did you take care of these requirement ? Please have look at release note of exchange 2010 SP2

or you can uninstall your exiting exchange 2010 and do a fresh setup of exchange SP2
wpstechAuthor Commented:
Yes, as noted all prerequisites were met, including enabling the "IIS 6 WMI Compatibility" Windows feature.

If I need to remove all instances without interfering with the 2nd Ex2010 box or any of it's AD related references, or without interfering with the Ex2003 servers, do i simply remove the corrupt Ex2010 server from the container using ADSIEDIT?  How do I handle the references of public folder replication and the routing group connector that was made between 2003 and this corrupt 2010 server?  
Madan SharmaConsultantCommented:
have you move the public folder replication from exchange 2K3 to this new exchange 2010 ? if yes then try to move the replication of public folder back to your e2k3. also move the mailbox back to ek3 if you have moved any from 2k3 to 2010. Also delete all test mailboxes.

Then try to run /mode:Uninstall  etc

this unistallation process will not effect your exiting e2k3 and after successful uninstall reboot your server. Prepare it for exchange 2010 SP2 and install it.
wpstechAuthor Commented:
as noted no public folder replication had occurred and no mailboxes were moved.  Running the uninstall will not work as the SP2 has corrupted the files and/or removed them.  The steps that were take required for the server to be rebuilt with a fresh OS install, the computer account to be reset in AD and the /m:recoverserver switch to be ran for a disaster recovery installation of Exchange.  Microsoft acknowledged that SP2 had issues and that this issue had been reported by multiple clients at their service/support site.  Their recommendation was to install Update Rollup 6 via Microsoft Update, which is what I did.

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wpstechAuthor Commented:
Additional research and confirmation from Microsoft support confirmed steps needed to resolve this issue
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