I have recently acquired a second-hand laptop.
The audio was working fine when I got it, both using it's own soundcard and also a DJ MIDI controller (which acts as an external soundcard).
Now however the audio apps (spotify, windows media player, youtube etc.) on the laptop have stopped being able to play music through it. The apps display that the sound is being played, the progress bar moves through the song to the end. However no sound comes through the speaker.
However if one goes into control panel to the Audio app, test sounds can still be played.