Hi chuggett,
Thank you for your reply, I regret that this has not resolved the issue.
Have you tried running the built in troubleshooter?
Press the Windows key + C to open charms
Type troubleshoot sound in the search bar and press enter
Follow the on screen prompts.
If this has not resolved it, you could try a restore back to a known good date. Using Microsoft System Restore (Windows 8)
If that has not fixed it, I suggest you do a recovery. Performing an HP System Recovery (Windows 8). During the recovery process you will receive a prompt to backup your personal files. If you have not done one yet, I suggest you do it now to prevent data loss. Restoring Files that were Backed Up Using HP Recovery Manager (Windows 8).
Please let me know the outcome.