Why is the theme from "Rockford Files" stuck in my head?

The theme from "The Rockford Files" is inexplicably in my head this morning, and I can't get it out. I haven't seen that show since it was on (The Seventies) and I never actually watched that show, I would always change channels when it was on. In fact, I don't recall every actually watching the show, but I must have because not only was the tune in my head, I knew what show it belonged to. The brain: just weird.