I know you said that you are certain that the file is already
in PCM format. But just for grins, you might try clicking Start
> Run... and typing sndrec32.exe into the Run dialog. Then press
Enter. The generic Windows Sound Recorder application should open.
Open the file giving you fits. Then click File > Save As... and
note what format is listed at the bottom of the Save As dialog next
to the Format: area. You may be surprised to see it's not PCM. Even
if it is PCM, click the Change... button. And this is all you need
to do! From there, just click the OK button to dismiss the Sound
Selection dialog. Then click the Save button to dismiss the Save As
dialog. You might wish to change the file name of the original .WAV
file in case you ever need it in the original format for anything.
Give that a go and let us know if it helps. Hopefully it