Extremely useful fact I have discovered: Where It's At, by Beck, is the perfect song, to permanenty erase anything annoying that is stuck in your head. It is more catchy than almost anything, so easily trumps whatever tune is bothering you, but doesn't loop, so transitions easily into an ending.
http://musicglob.com/wp-content/uplo...ere-its-at.mp3
Seriously, I am not even slightly joking. I've used (and told other people to use) this technique almost without failure for years. Start singing the opening keyboard parts (do, da-do do da DAH...) to yourself, and let the whole song play out, and tada! Whatever was stuck in your head is now gone. If you're not yet familiar enough with it to sing it through, come to this thread and play it, and hum along.