If someone has windows key, Then he can submit it to Microsoft site to download or get relevant ISO or DVD, But Microsoft did not offer product key after seeing your DVD media.
You can only restore lost product key, If you've link it with your Microsoft account, Otherwise you've to buy a new product key for any version of any OS, As I was in the same problem last week, So I searched at Google to find a cheap license key for Windows 7 Ultimate 64bit for my Lenovo i7 laptop