Missing sound files are usually down to downloading a "ripped copy" of a game, where additional files which aren't vital to the game's functioning are removed. I'm not accusing you of this, but be aware of that.
If that isn't the problem, try using benny's launching tool
with a fresh installation of the game, and then patch the game and copy the files to the hard drive via the utility. If it still fails, I'm really not sure. Do the sound files play if you try using a completely unmodified fresh installation of the game, running from CDs?