If you're having trouble getting your Lacie CD burner to work, get one of those DVD's that runs as cleaning program--mine stopped working and Lacie tech support suggested that I try it--it worked!
Ignore every one else, and do what I suggested, Linda--it is cheap, easy, and will be good--

You have a build-in soundcard that plays CD's/DVD's but in order to record the sound from your cassette, you need to some sort of analog audio input(I think you do have an input for a digital mike)--used to be the only way to do this was to install a soundcard--but you can't install one in an iBook, though because you have no card slots--not problem because now there are USB interfaces like iMic that eliminate the need for a soundcard--even folks who do serious computer-based recording and sound editing now no longer use soundcards, and instead use USB audio interfaces like mBox--