The theme was written by Glen A. Larson, the creator and executive producer of the show. It’s one of the very best in the medium—haunting, mysterious, and catchy as hell. He also co-wrote the themes for Knight Rider and Battlestar Galactica, among others. (Larson got his show business start in the 1950s as a singer and composer in the Four Preps.) For the third and final season, the format changed (Nancy Drew was dropped and the Boys found themselves working for the Justice Department) and the theme was very unfortunately jazzed up.
I’ve been making my way through Magnum P.I. (another Larson hit) and the The Hardy Boys for the last few months. The shows may be silly at times, and “uncomplicated” compared to today’s supposed “golden age of television,” but I find them cozy, fun, and deeply, refreshingly hopeful.
2 Warps to Neptune 
The Hardy Boys and Battlestar Galactica were two of my favorites shows when I was a kid. I started rewatching them a year or two ago, more for a laugh than anything else, but was surprised by how much I still liked them. They are solidly entertaining.
Having a lot of fun with The Hardy Boys. Just started season two. I watch the original BSG every few years. It’s no Star Trek: TNG, but the concept is genius and the sets, costumes, and effects are delicious.
My favorite show right now, believe it or not, is The Love Boat. I’m DVRing them off of various “retro” channels because only the first two seasons are out on DVD.