Cassettes no. Unfortunately the majority of songs out there are now on cd. A suggestion would be to download a P2P program, although those are illegal unless you pay for it. Napster may be an option.

You need to record the music from the tapes using an audio card with a two-channel, line level input. You connect the line level outputs of the cassette deck to the line level inputs of the audio card. You will need to record the songs one by one or you can record the entire tape in a single block, cutting it into individual songs using an audio editor. I use a very good audio editor called 'Audacity', which available from http://audacity.sourceforge.net/ . It is free and is available for Windows, Mac OS X, and Linux. You may already have a sound card with this capability installed in your computer. The card you connect your speakers to may also have line level inputs. Most of the SoundBlaster cards or integrated Analog Devices chipsets (SoundMax) can do this. But be cautious with the quality of these devices - they are not all they are cracked up to be in their advertising material. A semi-pro or pro-audio card will do a much better job. You probably won't find one at your local computer store, but you can find them them on-line or at a music store. I use an M-Audio Audiophile 2496 and find it works quite well for the price. The 2496 is a basic two-channel card and supports two analog line level inputs / outputs (up to 24-bit, 96 kHz sample rate), S/PDIF I/O, and MIDI. There are many other companies making suitable products as well.