I have around 500 cassettes/hours with very important educational material that I've gathered through the years and don't know how to transfer them to my computer, to be able to listen to them from there. I've tried to record them to an old mp3, as if they were voice, from the loudspeakers, but it doesn't work well, and it's too time consuming. Somebody could help me please? Thank you very much.
I don't think so, on a standard tape recorder/player. You either spend time, or money - this maxim stands in just about everything. Windows have a built in recorder, and your sound card might come with its own more elaborate one. I bet Mac has something of the kind, too.
And I don't think it would take years. Giving some leeway for getting it right and changing tapes, 500 hours of tapes will take say 1000 hours, which translates into 125 days with 8 hours a day spent on the task