Product keys are usually found in stickers, cards or labels inside the cases of purchased computer software. For online purchases, the product keys are typically emailed along with the invoice.
Popular programs that use 25-character product keys are sold by Microsoft, such as its Windows operating systems and Office suites. Every product key is unique to a copy of a software and typically required during installation. Users are advised to make a copy of their product keys for safekeeping so they can use them again whenever they need to reinstall their purchased software. If the product keys are lost, they can be recovered in several ways: downloading a key finder program, searching manually or contacting customer support.