The GetSecurityDescriptorGroup function retrieves the primary group information from a security descriptor.
BOOL GetSecurityDescriptorGroup(
  PSECURITY_DESCRIPTOR pSecurityDescriptor,
                             // address of security descriptor
  PSID *pGroup,              // address of pointer to group security 
                             // identifier (SID)
  LPBOOL lpbGroupDefaulted   // address of flag for default
);
 If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero. To get extended error information, call GetLastError.
  Windows NT: Requires version 3.1 or later.
  Windows: Unsupported.
  Windows CE: Unsupported.
  Header: Declared in winbase.h.
  Import Library: Use advapi32.lib.
Low-Level Access-Control Overview, Low-Level Access Control Functions, GetSecurityDescriptorControl, GetSecurityDescriptorDacl, GetSecurityDescriptorLength, GetSecurityDescriptorOwner, GetSecurityDescriptorSacl, IsValidSecurityDescriptor, SECURITY_DESCRIPTOR, SECURITY_DESCRIPTOR_CONTROL, SetSecurityDescriptorGroup, SID