Error: User xxx already Exists

DECLARE @UserName nvarchar(255)

DECLARE orphanuser_cur cursor for

SELECT UserName = name FROM sysusers

WHERE issqluser = 1 and (sid is not null and sid <> 0x0) and suser_sname(sid) is null

ORDER BY name  

OPEN orphanuser_cur

FETCH NEXT FROM orphanuser_cur INTO @UserName

WHILE (@@fetch_status = 0)

BEGIN

   PRINT @UserName + ' user name being resynced'

   EXEC sp_change_users_login 'Update_one', @UserName, @UserName

FETCH NEXT FROM orphanuser_cur INTO @UserName

END

CLOSE orphanuser_cur

DEALLOCATE orphanuser_cur

go

sp_change_users_login: Maps an existing database user to a SQL Server login. This feature will be removed in a future version of Microsoft SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use this feature. Use ALTER USER instead.

http://msdn.microsoft.com/en-us/library/ms174378.aspx

ALTER USER: Renames a database user or changes its default schema:

ALTER USER Mary5 WITH NAME = Mary51

ALTER USER Mary51 WITH DEFAULT_SCHEMA = Purchasing

http://msdn.microsoft.com/en-us/library/ms176060.aspx