Connect the Y end of the mini jack cable to the female "Line Out" or "Audio Out" ports on the stereo.
Connect the other end of the mini jack cable to the female "Line In" or "Audio In" port on your computer sound card. This port usually is color coded blue.
Turn on your computer. Open any Internet browser (e.g, Mozilla). Download and install the free Audacity audio recording software program.
Open the Audacity program. Click "Edit" and then "Preferences." Click on the "Audio I/O" tab. Select the device from which you want to record under the "Device" drop down menu under the "Recording" heading. Do not set this setting as Microsoft Sound Mapper if you're running Windows, since this is the default for output.
Plug in your stereo and turn it on. Cue up the cassette tape to where you wish to start recording.
Click the red "Record" button in the Audacity control panel located at the top of the Audacity window.
Press play on your stereo to start the cassette. Let the cassette play until you want to end your recording. Press stop on your stereo.
Click the yellow "Stop" button in the Audacity control panel.
Locate the scroll panel at the bottom of the Audacity window. Click on it and drag it to the right to get to the beginning of your recording. Find the point in the audio recording where the audio starts (this is visible on the graph for the track that Audacity automatically creates). Double click on the audio track graph just prior to this point.
Click "Edit" and choose "Select." Choose "Start to Cursor." Hit the delete key on your computer or click on "Edit" and choose "Delete" to remove any "dead air" at the beginning of your recording.
Scroll to the end of the recording and delete the dead air from the end of the audio using the method in Steps 9 and 10; choose "Cursor to End" instead of "Start to Cursor."
Click "File" and select "Save Project As" if you want to be able to edit the project later. Skip this step and proceed to Step 13 if you know you don't need further editing.
Click "File" and choose either "Export as MP3" or "Export as WAV." Enter the ID tag information if exporting as an MP3; these tags help your audio player identify the piece by items such as title, artist, genre and year. Choose a location in which to save the file on your computer and name the file. Click "OK."