If you use PDA to record some sound, the file format you get will be .pwi format. It is not a supported audio format for most media players, or audio converters either. After searching the Internet, I found the following work-around to convert the .pwi format to the mp3 format.

You need two tools before you start:

1. A Hex editor. I use PSPad editor.
2. An audio converter. I use Audacity.

Here are the steps:

1. Open a copy of the .pwi file with PSPad in Hex mode (just in case it does not work).
2. Delete everything up to the “RIFF” header (.wav format starts with “RIFF” header).
3. Your file should start with “RIFF” now. Save the file and rename it to .wav format.
4. Open the .wav file with Audacity and then export it to the .mp3 format.