The nature of music is that it strikes certain emotional responses when heard, and by definition, a 'pop' song will be equipped with the necessary triggers to repeat itself, and if you like it, to inspire you to buy it. Of course, as you point out, this can have an adverse effect if it is a song you dislike - I can hear Whitney Houston foghorning about always loving Yahoo as I type! The way to eliminate this is to try and avoid 'going towards' the song with your mind - think about something else quickly, and eventually your mind will loose its memory of the hook line it has picked up. Excuse me, I'm just off to punch a total stranger!