I recently downloaded some live music performances from the “Internet Archive”:http://www.archive.org/audio/ and they were in the Shorten (.shn) format. I found an easy-to-use “converter”:http://www.dbpoweramp.com/dmc.htm that will convert the files to the MP3 format.
The dBpowerAMP converter supports a multitude of “codecs”:http://www.dbpoweramp.com/codec-central.htm. If what you need isn’t built in, you can download what you’re looking for and install it.
It looks like a windows only package supporting Windows XP / 2000 / NT4 98 / 98SE / 95 & ME (and Linux through Wine).