If you haven't done so already, download the Card Manager software for the PS-02:
http://www.zoom.co.jp/english/download/ ... e/ps02.php
Use that to convert to wav - don't forget to specify 128/44 when you convert to wav.
Next, download Audacity:
For converting to MP3, you'll need the LAME MP3 encoder:
Put the LAME encoder dll anywhere on your computer. In audacity, you'll set it up to find LAME, a one-time deal, after that it knows where it is.
After converting your file(s) to wav using Card Manager, drag-drop them into Audacity and go the file, export, menu and select export project as MP3.
It is important to keep all the bit rates the same (starting with 128/44 makes that easy, see above) or you'll get chipmunks singing your song!
The above method works for sure, and I have never had any problems with it.
Audacity is a very powerful free program. LAME is free. You can't go wrong.
If you are on a Mac, I believe the software is already installed for doing the above - I believe you would use i-Tunes.