problem in reading the domain name under windows using c

#include "stdafx.h"
#include <windows.h>
#include <Winsock2.h>
#include <Lm.h>
#include <string.h>
#include <iostream.h>
int main()
{
    WSADATA D;
    int iReturn;
    DWORD size = 1000;
    DWORD count = 0;
    DWORD tries = 0;
    iReturn = WSAStartup(MAKEWORD(2,2),&D);
    if(0 == iReturn)
        printf("The sucess\n");
    else
        printf("\nThe error%d\n",WSAGetLastError);
    wchar_t *server = NULL;
    wchar_t *groupName = L"Workgroup"; // global group name
    DWORD rc, pref, got, total, resumeh = 0;
    GROUP_USERS_INFO_0 *buf;
    pref = 16; // start low, get more later
    buf = NULL; // important!
    do
    {
        pref *= 2; // bump buffer size
        printf( "Trying with prefmaxlen == %lu bytes\n", pref );
        if ( buf != NULL )
        {
            NetApiBufferFree( buf );
            buf = NULL; // important!
        }
        rc = NetGroupGetUsers( server, groupName, 0, (LPBYTE *) &buf, pref, &got, &total, &resumeh );
    } while ( rc == NERR_BufTooSmall || rc == ERROR_MORE_DATA );
    if(rc != 0)
    {
        printf("Duh! -- error %lu\n", rc);
    }
    for ( rc = 0; buf != NULL && rc < got; rc ++ )
    {
        printf("\nhai\n");
            printf( "%S\n", buf[rc].grui0_name ); // %S: cap-S toggles Unicode/ANSI
    }
    if ( buf != NULL )
        NetApiBufferFree( buf );
    return 0;
}