The company I worked for actually used a usb dongle. This was handy because:
- Our software was also installed on that USB Stick
- The program would only run if it found the (unique) hardware key (any standard USB key has that, so you don't have to buy something special, any stick will do)
- it was not restricted to a computer, but could be installed on another system if desired
I know most people don't like dongles, but in this case it was quite handy as it was actually used for a special purpose media player that we also delivered, the USB keys could thus be used as a demo on any pc, but also, and without any modifications, be used in the real application (ie the real players), once the client was satisfied
