Hi Renato Fajdiga ,
USE master
EXEC sp_addextendedproc xp_ndo_enumusersids, 'C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Binn\xp_ndo.dll'
GO
USE master
EXEC sp_addextendedproc xp_ndo_enumusergroups, 'C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Binn\xp_ndo.dll'
GO
GRANT EXECUTE
ON [xp_ndo_enumusergroups]
TO PUBLIC
GO
GRANT EXECUTE
ON [xp_ndo_enumusersids]
TO PUBLIC
GO
******you know that you need to have xp_ndo.dll copied into MS SQL BIN folder******
and also if u r using Windows 8 or 2012 check for u r UAC settings and you need to be admin .
And u need to have read write permisions to the bin folder
MOULI KAKU