냉무라고 하시니.. 저도 냉무로 답변을 할까 하다가... --;;

#include <nb30.h>

struct ASTAT
{
    ADAPTER_STATUS adapt;
    NAME_BUFFER    NameBuff[30];
};

AnsiString __fastcall GetMACAddr(int nAdapterNum)
{
  NCB ncb;
  memset(&ncb, 0, sizeof(ncb));
  ncb.ncb_command  = NCBRESET;
  ncb.ncb_lana_num = nAdapterNum;
  if (Netbios(&ncb)!=NRC_GOODRET) return "";

  ASTAT Adapter;
  memset(&ncb, 0, sizeof(ncb));
  ncb.ncb_command  = NCBASTAT;
  ncb.ncb_lana_num = nAdapterNum;
  strcpy(ncb.ncb_callname, "*");
  ncb.ncb_buffer = (char *)&Adapter;
  ncb.ncb_length = sizeof(Adapter);
  if (Netbios(&ncb)!=NRC_GOODRET) return "";

  return AnsiString().sprintf("%02X-%02X-%02X-%02X-%02X-%02X",
    Adapter.adapt.adapter_address[0], Adapter.adapt.adapter_address[1],
    Adapter.adapt.adapter_address[2], Adapter.adapt.adapter_address[3],
    Adapter.adapt.adapter_address[4], Adapter.adapt.adapter_address[5]);
}

MSDN의 예제를 참고한 것입니다.
그럼..