Add file to library doesn't add .WAV files to iTunes library
I'm running iTunes (11.1.3.8) on Windows 7 (professional). I originally created this library by importing and copying songs from an iTunes library on an older system (running XP). It's been a little while, but I'm pretty sure I made use of Add File to Library and Add Folder to Library when I did this, and that some of the files I loaded were .WAV files (which I then converted to MP3 in iTunes to save space).
Now, however, when I try to add .WAV to the library using Add File to Library, nothing happens. The files aren't imported. I can see that they're not showing up in Unknown Artist/Unknown Album as they usually would. If I use another program to convert the .WAV file to an .MP3 file (including the ability to add an artist name), the file appears in iTunes under that artist. (My library is organized by iTunes.)
My Windows preferences are set so that .WAV and .MP3 files are both opened by default with iTunes.
What am I missing? I suppose I can convert all the files before I import them, but I didn't think that was necessary.