It's the theme song from "Mickey's Christmas Carol." For whatever reason, Windows Media Player isn't loading the .ocx add-on correctly. (typical Microsoft, you know.) Save it to your desktop first, then play it from there. ;D
I encourage everybody to buy Classic Holiday Stories on DVD. Here's a link to it on Amazon.com. It's only $9. You can get it at Target for a similar price. It contains Mickey's Christmas Carol, Pluto's Christmas Tree(where chip and dale live in the tree mickey chops down and pluto notices them), and The Small One.
Here's a cleaner mix that I put together last month. I ripped it from the DVD. At the beginning of the film, the song's ending runs into the soundtrack, and at the end of the film, it starts about 2/3rds into the song. So I mixed both pieces and it turned out really nice.
Funny someone should mention this song, I happened to be transfering some of my Disney Christmas LPs to burn on CD and among the LPs was the Storyteller Picture Disc of "Mickey's Christmas Carol" and the song was on the LP. Of course, this was the re-issued version of the 1975 Dickens' Christmas Carol album but changed to fit the film.