Title music origin for Gnarls Barkley's 'Crazy'

If you've seen the film, you might have noticed it's theme song. The tune can be heard on every radio station in the world, cause it's been sampled by Gnarles Barkley for their smash-hit 'Crazy'. No wonder that song reminded me of spaghetti westerns in the first place! Here's the proof:
http://www.youtube.com/watch?v=5x6-xXzqChI