How does one copy cassette tapes to computer?


I have a friend who wants to save his recordings he has on cassette to his computer. Are there any products out there that could do this, and how would one go about it? I would be interested in knowing the answer to this myself. I know there are products out there for transferring vinyl to the computer, but what about cassettes?
learsfool
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Thanks very much for the responses, everyone! I will relay this info to my friend, and also possibly make use of it myself when I get the time!
I use a Nakamichi Dragon into an M-audio Delta 1010, running Steinberg Wavelab recording and mastering software. An M-audio Audiophile 194 sound card would be less expensive and almost as good. Unfortunately, many recent brand-name desktop computers lack an extra PCI slot. Aside from the playback cassette deck, the quality of your A/D converters will be the limiting factor. Unless you are a computer wizard, there is a steep learning curve to configure and learn to use this stuff.