This some beautiful violin/piano piece that I'd like to purchase, but I don't know who composed it and what the name of it is and am hoping someone in here can tell me.

I made an mp3 clip (about 1 minute) which you can download by clicking the link below. FYI, this clip is from the Movie "Bad Santa" but I couldn't locate this piece on the soundtrack.

Thanks in advance!

http://home.insightbb.com/~pixels/unknown/unknown.mp3

We all should keep in mind that movies usually have a composer compose a special score just for the movie, but often, they will use music from the masters. This sounds like a contemporary piece, most likely composed for the movie, but I have been wrong before. If you notice the middle, where the piano comes in, it has the characteristic tempo of a habanera, played with unusual chords, making me think that it was one of the preludes (No. 3 in book 2, I think) by Debussy. Sorry I couldn't be of any other help.

I found out what it is!

"Por una Cabeza", meaning in Spanish "by a head [of a horse]" is a popular tango song composed in 1935 by Carlos Gardel and Alfredo Le Pera. Gardel was more of the composer and Le Pera more of the lyricist.

The habanera was invented before the tango, I believe, so it does make more sense of calling it a tango. Great job on the research!