Good ol’ Limewire. Where you could download Limewire Pro… on Limewire.
Fun Side Story: I had one of the first digital video camera’s and pulled an epic goof on Limewire. I put a file in my upload folder titled “Blink 182 – First Date (Official Video)” a few days before it aired on MTV. A shit ton of people downloaded it, and it was a 30 second loop of me eating a sandwich to the Space Jam theme song. Fun stuff.