from Wikipeida:
"In computer networking, a Media Access Control address (MAC address) or Ethernet Hardware Address (EHA), hardware address, adapter address or physical address is a quasi-unique identifier assigned to most network adapters or network interface cards (NICs) by the manufacturer for identification. If assigned by the manufacturer, a MAC address usually encodes the manufacturer's registered identification number."
Detecting MAC Address using C application
Getting MAC Address (NetBIOS Method) within C/C++-program in Windows2000: msg#00095