I can’t take credit for this good article – it’s from the Evil Sensei @ http://evilsensei.blogspot.com
Have you ever encountered the following error when attempting to reinstall Exchange Server into a domain where it was previously removed?
The component “Microsoft Exchange Forest Preparation” cannot be assigned the
action “ForestPrep” because:- To install the first Exchange server in a domain, or to run setup in
“/ForestPrep” mode, you must be an Exchange Full Administrator at the
organizational level. You must use an account that has been granted the Full
Exchange Administrator role on the Exchange organization using the Exchange
Administrative Delegation Wizard.
An incomplete deinstallation of Exchange Server objects in the Active Directory. Exchange Server stores much of its configuration information in Active Directory – specifically in the Configuration partition. If any of this information remains in Active Directory, Exchange Setup will fail.
To reinstall Exchange try this workaround:
If no other Exchange 2000 or 2003 servers exist in your organization you may remove any latent entries from Active Directory by using ADSI Edit.
WARNING: If you use ADSI Edit, LDP, or any other LDAP version 3 client, and incorrectly modify the attributes of Active Directory objects, you could cause serious damage to your directory. These problems may require you to reinstall Windows Server, Active Directory, or both. Modify these attributes at your own risk.
Note: To make ADSI Edit available, install the Windows Server Support Tools from the Windows Server CD ROM or other source location by running SUPTOOLS.MSI from the SUPPORTTOOLS folder. Add ADSI Edit to an MMC SnapIn to complete the following steps:
Open ADSI Edit
Right click ADSI Edit in the left pane and choose Connect To … The Connection Settings dialog will appear.
In the Connection Point window, choose Configuration from the Select a well known Naming Context list. Click OK. The Configuration node will appear under ADSI Edit.
Expand the Configuration container: cn=configuration, cn=services, cn=Microsoft Exchange.
Under the Microsoft Exchange container will be a container with your organization’s name. Right click the container and choose Delete. Confirm the deletion and close ADSI Edit.
If there are multiple domain controllers in your forest, wait until replication has reached them all or manually replicate the change to all domain controllers in the forest.
You will now be able to re-run Exchange Setup.
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