During the exchange 2007 setup in Readiness Checks, it tells me that "One or more Active Directory Connectors have been found. Please remove all Active Directory Connectors before installing Exchange 2007." However I searched all exchange server (we only have one) in both add/remove programs and services, or under the system manager menu, I do not see any Active Directory Connectors. Why is this happening? Am I missing something? And I know what Active directory connector is!!!

Active Directory Connectors are probably remnants from a previous migration. Check your DC's for the connectors too. Otherwise use ADSI Edit to cleanup the remnants from your AD. The following article could give you some guidelinesand guidelines of what to look for. http://support.microsoft.com/kb/319486