Windows Key Viewer lets you find your Windows product key easily.
As you know, this is useful when you can't find your product key and need to reinstall Windows.
Windows Key Viewer is portable, requiring no installation, and easy to use. Once it displays your product key, you can write it down, old school, or copy it to the clipboard. You can also email it to yourself, although that's probably not the best plan unless you have to.
Please note that you are in the Covert Ops category on MajorGeeks. Covert Ops is a play on the original definition, "an operation that is so planned and executed as to conceal the identity of or permit plausible denial by the sponsor." In other words, you're doing something in Windows that it or your security software will consider suspicious. Hence most files in Covert Ops will be flagged as potentially malicious.