STEP 1: Get MusicMatch software: http://www.musicmatch.com/
Shop for pirated versions around manila. Plenty around.

STEP 2: Using a double-ended audio headphone jack, connect one end
of the jack to the headphones or "audio out" of your
cassette tape. Connect the other end of the jack to the
"Line in" of your computer.

STEP 3: Tinker with the recording settings in MusicMatch to accept
audio from the computer's "Line in". Set the audio compression
to MP3.

STEP 4: Click the "record" button in MusicMatch, then press the "Play"
button from your cassette tape to play your tape.
(Make sure it's not the wiretap tapes you are recording)

STEP 5. Click the "stop" button in MusicMatch and the "stop" button
from your cassette tape when done.

Your tape audio is now in MP3 format.