Have you tried creating a view to AD? You can use the following:

CREATE VIEW [vADUsers] AS

SELECT samAccountName AS TM_Number

,displayName AS Workstation_User

,Department

FROM OPENQUERY(ADSI, '

SELECT samAccountName, displayName, Department

FROM ''LDAP://DC=<DOMAIN NAME>,DC=<DOMAIN NAME>,DC=COM''

WHERE objectClass=''user'' AND objectClass<>''computer''

')

If that goes okay you can query it to see if you are talking to AD.