After deploying Microsoft Exchange 2010 in your existing Exchange 2007 organization you might face the following error from using either Exchange Management Shell or Exchange Management Console
An IIS directory entry couldn’t be created. The error message is Access is denied. HResult = –2147024891
The error looks like this in EMS
As the error message shows this is due to a permission error but on the Exchange 2007 side and not on the Exchange 2010!
To solve this simply add the “Exchange Trusted Subsystem” group to the “Local Administrators” group of all your Exchange 2007 servers.