Have you taken the time to listen to the music that is played in the background of Nathan and Haley scenes. Well a few weeks ago one of the One Tree Hill websites had the song that is called 'love theme' available for download.
So needless to say I couldnt help myself. Its only a minute or so long but I was able to put clips and voice overs from the first all the way to the third season.
I hope you enjoy this small video.
NOTE: I dont have the NH Theme anymore. my computer died and I lost all of my music so I am sorry that I cant help you. I got this song a few years back when it was available for download on OTHs Main website.