Ok if you are using some sort of a stereo cassette thing that has rca outputs, you'll need to buy a cable form Radioshack that has a headphone jack on one end, and two rca male plugs on the other. You'll need to plug it into your Line in, or microphone port on the back of the pc. As far as actually doing it, its very simple, start the analogue converter program(Start, All programs, Plus!, Analogue converter(or something like that),you select where to find the audio(Select line in, or microphone, depending on where you plugged it in) And then play the music so it can set itself. Then rewind the music and hit play and record on the program. It will automatically record everything and stop recording when your tape stops playing. It will also devide the tracks for you. It's very easy to use.
Make sure you buy the Plus! Media Center Edition, not the other Plus! Edition...