Use the HP Recovery Manager to reinstall the audio driver. Click on the start button and type in HP. The choices of HP Support Assistant or HP Recovery Manager should appear. Click on HP Recovery Manager and the following window should appear.
You have a choice here to also click on Microsoft system restore. Chhsing that will allow you to choose a restore point dated before the audio issue began.
If you choose Drivers and Applications restore you should see a window like the one that follows. Click on the box next to the IDTHigh-definition (HD) Audio driver and then click on Install in the lower right bottom corner. Recovery Manager will reinstall the driver. You may need to restart the notebook.
Test your sound. Post your positive or negative results here.