do a forum search on the word "sound" from about a week ago until today. there's a thread about this. basically you open the sound file in a program like Wavosaur or Audacity and save it again, making sure it's a .wav
I would worry about this if the files were 40 or 50 MB to start, but at a few hundred kilobytes or a megabyte to begin with, there's no appreciable difference to worry about.