Peeking into the rock

So I started recording my songs.  That is, songs I sing.  I have a bit less than forty recorded.  However, as of today -- not yesterday, when everything was behaving normally -- I can only hear the songs I recorded, period, no other sound files, and only when I have the headphones plugged in.

Previously, if I unplugged the headphones, the speakers would work normally.  I have checked what I know to check: connections, volume/mute settings.  I know something changed somewhere because when I test the speaker jack a new dialog box comes up I've never seen before.  It's a RealTek settings popup I've never ever ever seen before asking me whether I've plugged in a headphone, a line out, or a rear speaker.  By clicking around in its settings, I was able to tell it to stop muting the speaker when the headphones are plugged in (though I must reiterate that the problem is not when the headphones are plugged in, it's when they are not).  No change to the basic problem.  I don't even know where to begin troubleshooting this.