Co-Existence of Exchange 2010 with Exchange 2007. EMC Error "IIS directory entry couldn't be created. The error message is Access is denied"

Problem
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After Adding your Exchange 2010 Servers into an Organisation which has any Exchange 2007 servers present. When you try and Manage the CAS Servers through the Exchange 2010 EMC you will recieve the below error

" IIS directory entry couldn't be created. The error message is Access is denied"

Solution
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Add “Exchange Trusted Subsystem" group  a member of local admin group of ALL Exchange 2007 servers in the entire organisation.