Many times I thought about getting riddle of my old cassette tapes. But finally I decide to transfer them to the mp3 format. The cost was very low and worth my time.
You can download an open source software like Audacity for free, and buy a cassette player with USB port on eBay really cheap. I was surprised how good the recording transfer was. So far I have transferred ten cassette tapes to the mp3 format. I am very happy with the results.