This is some information I found about Anneliese on the internet. I'm pretty sure the tapes I found are of the same girl.
Wikipedia:
http://en.wikipedia.org/wiki/Anneliese_Michel
90 minute audio recording that sounds a lot like the recordings I found:
http://kath-zdw.ch/maria/Download/michel_90.wma
Creepy YouTube video that shows some stills of Anneliese along with some of the audio of the exorcism.
