sound issue

ok i'm a total noob here so if this is already posted i have no clue what 2 search for. im trying to watch a720P movie with 5.1 WMA Pro audio and all i get is backbround music (no voices). i turned on downmixing already and no change. i get this issue on my 1st gen MacBook internal speakers and even when i hook it up to my 5.1 stereo system via 3.5 mm. i know i'm missing something here but no clue what