Mio DigiWalker A701 User Manual page 138

On the "Select Additional Tasks" screen, scroll down and make sure
that AMR under Decode the following audio formats with ffdshow is
selected.
5. When the installation is completed, click Finish.
Before playback, you need to copy the *.3gp files from the \My Device\My
Documents\My Pictures folder of A701 to the desktop computer using
ActiveSync Explorer. Then you are ready to play back the *.3gp files on your
desktop computer using either Media Player Classic or Windows Media Player.
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