If you are setting up a new SQL Cluster or any application/service that requires the DTC cluster service, and you get the following error...

<span style="color: #ff0000">"object already exists in Active Directory"</span>

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...then you either need to choose a new name for the DTC cluster service, or you can give the cluster computer name object in AD Full Control over the DTC cluster computer object.

For example, if you have the following setup...

Cluster01 - Node
Cluster02 - Node
Cluster00 - Cluster Name
Cluster00DTC - DTC Cluster Name

Find the Cluster00DTC computer object in AD and view it's properties.  Go to the 'Security' tab and add the 'Cluster00' computer object and give it Full Control.  Run the DTC Cluster configuration again and it should work now.