Remove duplicates from Left Outer Join

Hi -
How do I remove duplicate Usernames from the query below.   I changed the query from a cross join to a left outer join to eliminate massive amounts of records.   Now I have the issue of retreiving multiple usernames (I'm grouping by MEMBEROF in the crystal report)

WITH EmployeeList AS
(SELECT DISTINCT   A.DistinguishedName,
                      A.AccountName,
                      A.DisplayName,
                      A.Type,
                      B.MEMBEROF,
                      B.USERNAME
FROM         ADUsersAndGroups A                
LEFT OUTER JOIN GROUPS B ON A.DistinguishedName = B.MEMBEROF
                 
UNION

SELECT DISTINCT  A.DistinguishedName,
                      A.AccountName,
                      A.DisplayName,
                      A.Type,
                      B.MEMBEROF,
                     B.USERNAME
FROM         ADUsersAndGroups A
LEFT OUTER JOIN GROUPS B ON A.AccountName = B.USERNAME)
SELECT * FROM EmployeeList
WHERE DisplayName is not NULL;


I'm trying to acheive the following output in the report:
Where user's are grouped by groupname.
MEMBEROF  (GROUPNAME)
          USERNAME (USERID)        DISPLAYNAME (User name)


However, I'm currently getting output were Display name is blank or populated with group information and the Username is diplaying multiple times.

Any help would be greatly appreciated.    Thanks!!  Mojeaux