title: What's a good way to uniquely identify a computer?
body: <p>I'm developing some desktop software for a client to resell.  The client wants to restrict the software so that the registration code will be specific to one and only one computer.</p>
  
  <p>Besides using the MAC from the network card, does anyone have any other techniques (that work on both Windows and Mac OS X) for uniquely identifying a computer?</p>