The simple answer is that you simply cannot rely on this value to do this. There is no solution.
What you need to do is find another way to register your application. Perhaps you could gather information on multiple parts of a machine and then generate a hash from those values so that as long as one of those components exist you get a valid result. Save the hash at that point.
My personal perspective is that tying a piece of software down to a specific machine is in no way a good way to register an application, so I would suggest looking to do this in a completely different way.
To learn a little more read this