You are probably in need of the metaflac.exe file which comes bundled with the flac distribution. Go here for the latest bundle. Unzip it and put metaflac.exe in the same directory with Flac Frontend.

Are you sure you know why you are clicking the Fingerprint button in the first place? If you downloaded the files you don't need to make a fingerprint except for future use. What you really want to do is verify that the files you downloaded match the fingerprints that came with it. For that you need a program called Md5check. Check my website for more about that one.