Plug a 1/8" stereo male plug into the line out (or possibly speaker out, whichever works best, try line out first. If line out is a no-go try speaker out, but keep the input switch on your tape cassette low, initially.) of your soundcard, and plug the 2 RCA right and lefts into the input of your tape deck. So - an 1/8" stereo male to 2 mono RCA's. Hit record/pause on your tapedeck, hit play on your mp3 player, set levels on the deck and your off.
