I got a WAV file, which I know is extracted from ac3_encoded AVI file. It can't be played by foobar2000, but no problem on Windows Media Player. I guess it should be matter with ac3 encoding or something. I don't know much about this.

Is there any handy tool I can convert this kind WAV so I can play it by foobar2000?

I would guess it actually contains compressed data, and that WMP uses ACM to decode it. Opening and saving it in an audio editor would probably fix that, but you should see filesize blow up, too.

Thanks, Garf!
With foo_ac3.dll and rename the .WAV file to .AC3 extention, it can be played now.