In reply to handofgod:
I did this recently with some tapes from the early nineties. with good results. You could capture the audio as a wav or mp3 file on a PC or Mac, split it into tracks (if appropriate), and then burn the file(s) to a CD. This process is pretty straightforward.
Best approach is to get a USB cassette player and use the free Audacity sound editing software. I got this cassette player new from Amazon (£18):
https://goo.gl/6VBfBg. You can download Audacity free from here:
http://www.audacityteam.org/download/. A simple workflow for capturing the audio is here:
https://goo.gl/UmWvyB. Using a USB player keeps as much of the process as possible digital, which improves the sound quality.
Alternatively, you could connect the headphone socket of a non-usb player to the microphone socket of a PC, and use Audacity to record from that. This is probably going to give sub-par results as the circuit is mostly analogue, and most PC sound cards are relatively poor at audio capture. If you do go down this route then you might want to invest in a screened audio cable, and experiment with playback volume levels.
A couple of tips: Keep the cassette player away from mobile phones while the tape is playing, as they can produce interference. Also, before playing the tape, equalise the tension by FF-ing it to the end and then rewinding it.
Hope that's useful.
Post edited at 16:51