The Hydra 2004 Rebetiko CD ROMs.
By the end of the 2004 Hydra conference, I had 1.6 GigaBytes of mp3 files recorded on my Archos Jukebox Recorder. This was far too much to put on the internet for download, so I used to sell copies of the files on CD-ROMs. Nobody has bought any of these for ages, so I have stopped selling them.