Ok, recently I had this problem on a desktop computer with external speakers. I know that seems like a different problem but I actually think it's the same and that it's shown me what the issue was. I recently started plugging in my speakers into every
jack on my soundcard to try and figure out if any of them worked. And it sort of did when I plugged it into my headphone jack. But not AFTER I plugged it in. Only when it was partially plugged in. This told me something was wrong with the sensor on the headphone
jack NOT ANYWHERE ELSE IN THE COMPUTER. Basically, there's a part of the headphone jack that tells the computer to send sound out the headphones instead of the speakers. This, basically makes your computer choose between one of two options with the deciding
factor being whether or not something's plugged into your headphone jack. So I jiggled around a headphone plug in the jack and sure enough, I soon got normal function again. Headphones in, sound comes through headphones, headphones out, sound comes through
speakers.
If this doesn't work, consider finding someone good with hardware and replacing the headphone jack on your computer.