I am having a very big problem. That is 'How to Create License for my software'. OK, Think this is my License key - 12345YW when the user enter this license key, the software should allow him to use the software. All right, once the user enter the license key, my software must remember he has entered the valid key, right?(because from next time onwards, it don't have to prompt license dialog) My question is, How can I make my software to remember the user had entered the license? In windows based apps, what most of they do is entering an entry to the windows registry. Can I do the same? (Then what about Ubuntu and Mac? Free Win4lin Download there. ) I thought of writing a.txt file so m software can read it and find whether license is entered or not.