Use the Management Class object in .NET.
ManagementClass oMClass = new ManagementClass ("Win32_NetworkAdapterConfiguration");
ManagementObjectCollection colMObj = oMCLass.GetInstances();
foreach(ManagementObject objMO in colMObj)
{
Console.WriteLine(objMO["MacAddress"].ToString());
}
Makes sense?
Andy
You might want to also add
Console.WriteLine(objMO["Caption"].ToString());
to your test before the mac address so that you know which devices you are looking at.
Also, don't forget to use try/catch blocks on these as a NullPointerReference will kill the app.
Andy
Unsolved 
