preparing Active directory for Exchange 2010
Follow the steps below to prep your AD for exchange 2010. you will need enterprise admin rights to perform this.
From a command prompt, and using setup.com(from exch2010 cd), run as follows and in order:
run this, if you still have remnants of exch2003 in your organization
setup.com /PrepareLegacyExchangePermissions
setup.com /PrepareSchema
setup.com /prepareAD
setup.com /preparedomain