Sound Out of Only One Speaker

I have had this annoying problem with my Asus G50VT laptop since I got it, but now it is driving me up the wall. The basic issue is that sound only comes out one of my external speakers. The speakers themselves are 100% functional as I have tested by plugging them into other computers, and I have since bought two different types of external speakers thinking this would somehow fix the problem. The headphone jack itself is fine too - I can hear stereo sound whenever I plug in some headphones. But for whatever reason, there is no sound coming out of the right-side speaker (it's always the one with the volume controls that doesn't work).

Is this a settings problem? I would not be surprised if it is something dumb like the right speaker being disabled or whatever. I have updated drivers and all that (using Vista). I cannot help but think this problem stems from this laptop not having a formal audio-out jack versus a headphone jack, although I suppose they could be the same sort of thing. Any help would be greatly appreciated, as I cannot think of how to word the problem better for things like Google or forum searches.