Winamp? As above but ensure .wav is ticked, although you'd normally get an error message telling you the file type is not supported.
Perhaps a silly question, but we must eliminate outside causes, do these .wav files play in another player? It is possible there is some corruption or the sample rate is not supported. Try playing the Windows start sound found in C:\Windows\Media folder. My suggestions are what I would try myself. If incorrect, I welcome corrections to my rather limited knowledge. Andy.