4 track tape cassettes?
Isnt that a normal cassette tape?
I used some really cheap recording software. Went out my tape deck via RCA conx, then converted that to stereo 1/8 inch in (avail at radio shack) into the line in/ mic on my pc. Just tell the recording software which input you are using.
If its a tape from a 4 track recorder and you tried playing it back on a normal tape deck, it probably will play back very slowly and at a much lower pitch. You may need to bring it back up to speed and pitch using some software. Or if you can, mix it down on the 4 track recorder first.