Taking a video and adding music to it?

I have this crazy anime video with lots of violence but no music or sound. I'd like to take this video (~1hr long @ 650MB) and put my own music in there!

Any freeware options? If not, maybe something cheap so I can pick it up when I have some extra cash (I had to buy an external tonight so Im broke) because I want to get into basic editing

 

It's an .AVI movie

 

Does anybody know how to take a movie and add your own music to it? That is all I need. I have searched for a bit on the interwebs and even came across a post by someone on Notebook review asking the same thing. No luck for either of us

iMovie does not work as it doesn't accept AVI or even Quicktime. It's DV only I'm reading. And at any rate, I really want to avoid iMovie at all costs.

Any other free (or even paid *cringe*?) apps out there that can do this?

It seems simple enough of an idea.

Movie file -----> Add my own music track in the background ----> watch the movie with my music.