Hey paucoin,
I'm sorry you're running into this audio issue. This seems like a software problem. There are a couple of things you can try.
In Playback Devices, which item listed is the Default (has the green checkmark)? Try setting Speakers as the default by selecting it and clicking the Set Default button.
You can also uninstall and reinstall the Audio driver.
1. Click the Start button
2. Type 'device'
3. Click Device Manager
3. Expand Sound, video and game controllers.
4. Double-click on Realtek Audio to open Properties
5. Click the Driver tab and let me know what version number is shown there.
6. Click the Uninstall button and when prompted, Restart.
The computer will restart and Windows will detect and reinstall the missing driver on its own. Let me know the driver version number and the results of those steps when you get a chance :)