Had the same problem myself last year, I've been trying to think how I solved it but I can't remember exactly. It was something to do with the windows sound controls, I can remember that much so have a look at them, it was either something being muted or I needed to add something to the recording section of multimedia for example enabling the audio in control. Sorry its a bit vague but I remember that it was something pretty simple and I kicked myself when I realised what it was. Good luck.
PS If I do remember exactly what it was I'll post you back.