The product can be used on a single computer at a time. You can't use two instances with the same license of the program simultaneously. If you don't have your license anymore, you can log in to the customer area on the official website. By doing this, you will be able to obtain the license again and use it on your new computer. If you have difficulties regarding this, it's advised to contact the developer for further support. To be noticed that you need to provide a proof of the purchase.