The following code is a working example for determining the MAC address of your network card.

Imports System.Net.NetworkInformation

Public Class Form1
  Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
    MessageBox.Show(getMacAddress)
    End
  End Sub

  Function getMacAddress()
    Dim nics() As NetworkInterface = NetworkInterface.GetAllNetworkInterfaces()
    Return nics(1).GetPhysicalAddress.ToString
  End Function

End Class