The Magical Jelly Bean Keyfinder is a must have software. The freeware utility retrieves your Product Key used to install windows from your registry. It also provides a community-updated configuration file that retrieves product keys for more than 300 other applications. Additionally the software enables you to retrieve product keys from unbootable Windows installations.
Both Windows 7 and Windows 8 are supported as well as all previous Windows versions, including Windows XP, 2003 Server, 2000, NT, ME, 98 and 95. The Keyfinder is not a key generator. It reads the registry and extracts the key that was used to install Windows.
It is free to download from this website.