How to Fix Audio Issues with ASRock Motherboards and Windows 8 / 8.1
To resolve this, ASRock has released a little known fix which, after executing, will make a change to the operating system to allow audio to play.
The fix can be downloaded below:
Simply run the executable and reboot the machine.
This worked for my P67 Transformer motherboard.
Disclaimer: I can accept no responsibility for any damage or data loss caused by the installation of this fix.