My mom and I were major league Ozzy Osborne fans, and at the time I began learning guitar in 1986, she was hooked on Blizzard of Ozz so I ended up learning Crazy Train first. Even to this day, when I'm in the mood to play with my effects pedals for different tone, I will use I Don't Know--because the slow portion in D-major sounds SWEET through a Flanger and a little delay (just the way Randy played it live on his Gibson). I LOVE it.