I'm a Big Sister, and I'm a Girl, and I'm a Princess, and This Is My Horse is the third in a series called Riverrun by Underworld, released on 5 June 2006 online. The download-only package is a .zip file containing a 192kbit/s encoded .mp3 file, a 6-minute QuickTime slide-show of black-and-white photographs set to ambient sounds, and a PDF of the CD insert.
I'm a Big Sister... is originally delivered as a 30-minute, 34-second audio file titled "Audio.mp3". Track names are taken from information at http://www.underworldlive.com/ . The track times listed are estimated by listeners.