Check COA (Certificate of Authenticity) Sticker We collected 7 ways that are efficient and you may try any one of them to find the Windows 7 product key: So how to find the product key on your old Windows 7 computer? Move on, and you'll get the answer in the next part. Virus infection or malware invalidate Windows 7.OS crashes, Windows 7 gets reinstalled and needs reactivation with key.Windows 7 expiries and needs reactivation with product key.Why is that? Here is a list of cases that you may need a Windows 7 product key: However, to some Windows 7 users, it's still necessary to record and keep the product key. As time goes by, Windows 7 is no longer supported by Microsoft anymore. Windows 7, as a classic operating system, attracted quite a lot of fans when the system was first released. On this page, we'll take Windows 7 as an example to present 7 reliable ways for you to follow and find the Windows 7 key successfully on your own. Windows key, also known as Windows product key, is normally used for activating Windows operating systems on computers.