Well, I'm not sure what your problem is. It may be this: For some reason, the evil_ending.wav will play correctly, but will not extract. Ditto for 57.wav (the good ending) and the credits.wav. Also, the loadingscreen.wav or whatever it's called will hurt your ears even to play, let alone decompress. A shame, too: I want the cheering spectators for the end of my JA level.
And trust me, it's not because of a slow system that they don't decompress. I have upgraded my computer significantly, as much as T3 at least, to play KotOR, not to mention LotR: RotK and a few other large games. Maybe it's double-compressed, I dunno. Worth an experiment, I suppose.