One of the first commercial mistakes I made, was to develop an application over a period of 4 months (it wasn’t that big an app), and not have any protection on it. The client was, emollient and friendly. He stated that his prime requirement, was he have a working demo. In my naiveté I supplied him with a fully working copy. It will come as no surprise that it was the last I ever heard from him. Trust no-one!
There is a myriad of choice when it comes to approaching this subject, but something that may appeal to you is Microsoft Software Licensing and Protection. There is an introductory video and the option to trial the utility, very useful indeed!