Have a look at your audio files...have the extensions changed to .zip? If this is what's happened, you've probably got a virus.

Update your AV & do a scan, see if any nasties are found. If not, try this one: AVG Anti-Virus Free Edition. Download it, update it & see if it finds a worm (Delf.ATB).

You might want to have a look at this thread: files from limewire converted into zip files

WARNING: Viruses on network you should be aware of!