

There is a possibility that the connection between your audio board and the internal speakers has been severed.

You will also see from your volume control centre that your computer is stuck on headset mode like shown below (headphones do not show up in windows 7). If the sensor does not reset when you take out the audio jack then your computer while think an audio jack is still inserted and not play any sound through the internal speakers.

There is usually a spring-mechanism sensor on the audio jack that detects when an audio jack has been inserted and when none is present.
