Private Function SystemSerialNumber() As String
        ' Get the Windows Management Instrumentation object.
        Dim wmi As Object = GetObject("WinMgmts:")

        ' Get the "base boards" (mother boards).
        Dim serial_numbers As String = ""
        Dim mother_boards As Object = _
                wmi.InstancesOf("Win32_BaseBoard")
        For Each board As Object In mother_boards
            serial_numbers &= ", " & board.SerialNumber
        Next board
        If serial_numbers.Length > 0 Then serial_numbers = _
            serial_numbers.Substring(2)

        Return serial_numbers
    End Function