You can also REGISTER your program, and let others take care of the security. The harder you make it to copy, the harder the bad guys will try to crack it. Get a HARDWARE DONGLE, sell it to each user, and the program won't run without it. That's how MUSIC RECORDING SOFTWARE woks. Except that you can register a bunch of programs into one dongle, and move it to different devices (that you own and have another copy of the software)