software problem or hardware problem?
are the speakers blown and frozen solid?
i wouldnt actually test them with audio from a different source, but maybe you could use a multimeter to grab the ohms.
if it is software, well it is a wrong setting because of you or a virus?
maybe the soundcard circuit for the speakers is dead?
i would think there are two amps.. one for the speakers and one for the earphones.
lots of times those laptop speakers are special enough to be very different than headphones.
meaning the ohms (impedances) of the speakers have the battery life in mind and/or are simply significantly different than usual.
cant find the exact answer to your question from here (not that i could do it all anyways)
maybe you can take apart the laptop and use a multimeter to verify if any electricity is going to the speakers.
sometimes when speakers are blown they seize up and wont play any sounds, even though there is electricity going to them.
it isnt an uncommon thing for people to blow their laptop speakers.
maybe when you take it apart you find that somehow the connector magically became unplugged.
you'd be lucky to find such a thing.. but if you dont get in there to look, somebody else will (and it might cost some money).
just think.. if your laptop speakers refuse to work for whatever hardware reason, a new soundcard probably wont play audio through those laptop speakers anyways.
you usually have to wear headphones or get some amplified speakers.