Check out this Freeware that I just came across (hat tip to Alec)
Ever thought ‘what is this song?’ Let Tunatic hear it and you will get the artist's name and the song's title within seconds. Tunatic is the very first song search engine based on sound for your computer. All you need is a microphone and Internet access.
Tunatic is freeware.
i think when you first install maybe the application needs you to reboot but doesn't tell you that you have too.
So far i give it a B-
Mislabeled details on one of my tracks and anything half eclectic it fails miserably but for something thats free - not half bad.
Interestingly it doesn't actually allow you to "provide details" once a song lookup fails to find the song - you think it would grow the library exponentially if you crowd sourced the details.
But hey for free who can complain.