The product ID will be different when you change your hardware or your operating system. If it’s on the same computer, you can ask for a new registration code by sending them your new product ID, they will generate a new registration code for you and disable the old one. One license is valid only for one computer. But multiple users can share one license on the same computer. If you need more licenses for installation on multiple computers, you can get a discount of at least 30% OFF on further purchase.