Open ADSI Edit and go to:
CN=Configuration,DC=DOMAIN,DC=LOCAL CN=Services CN=Microsoft Exchange CN=EXCHANGE_ORG CN=Administrative Groups
Exchange 2003
CN=First Administrative Group
Exchange 2007
CN=Exchange Administrative Group (FYDIBOHF23SPDLT)
Exchange 2010
CN=Exchange Administrative Group (FYDIBOHF23SPDLT) CN=Servers
You can also remove single objects of a server like Public Folder Database
.