Here's the breakdown:
* The song used in the show: "Carry On My Wayward Son" by Kansas. This is the iconic song that plays as Dean drives away with John, leaving Sam behind.
* The song listed on iTunes: "The World Is On Fire" by The Wickermen. This is the song *actually* featured on the soundtrack album released for Season 1.
Why the difference?
This is a common occurrence with TV show soundtracks. Often, the music used in the final cut of an episode is licensed for a limited period, and the producers cannot include it on the soundtrack album for copyright reasons. They then replace it with another song that has similar vibes and is available for licensing for the album.
In this case, "Carry On My Wayward Son" became so synonymous with the episode and the show itself that the difference went largely unnoticed by many viewers.
It's a good example of how the music used in a TV show can become a significant part of its identity, even when the actual song used isn't the one officially released.