What program did you use to make the sound file? I use Audacity (free from download.com) as a sound editor and it opens most formats--it gives and error when trying to open your file, even though the WMP seems ok with it.
Update: Actually, I just noticed that the bit-depth of your sound file is set at 4-bit. Try opening it and exporting it as an 8 or 16-bit format and see if that resolves it. I think 4-bit and maybe also 32-bit) are out of range for DirectRT.