Cannot hear sound from Dell Inspiron 1420

My speakers were working just fine. All of a sudden, I couldn't hear a thing. I can only hear audio if headphones or external speakers are plugged in. Without them, I hear nothing but my Volume Mixer shows my music is playing.

I opened up the SigmaTel Audio Control panel and it says my headphones are plugged into one jack, but they're not.  See for yourself in this picture:

I have tried reinstalling the sound drivers, toyed with sound settings and even performed a system restore. AND STILL NOTHING.

HELP!