How to secure .net window application

Question

I have used many method to secure vb.net window application but i could do this. My intention is that before my application to be installed on any client machine, they need to put one licence key and that licence key should be generated based on Computer's hardware. To solve it, i used machine's Serial Key method, but sometime some machine doesn't produce it. I also used Machine's MAC id but i couldn't do it.

Help me!