Make sure that MP3 files can be played in Windows Media Player.
Make sure there is a L3CODECA.ACM file installed on your system in the Windows/System (or WinNT/System32 or equivalent folder).
Make sure the LAME_ENC.ACM and the CTMP3.ACM files are not installed. These files have been known to cause decoding problems.
Try renaming them if a search finds them.
Make sure MP3 is enabled/checked in Windows Media Player.
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