After a clean install of Windows 8 I was not able to have sound from external speakers connected to a docking station.

Install drivers from HP, reboot.

From the HP website I downloaded the drivers IDT Sound drivers but the installation return : Not a compatible Hardware.

2 options.

Option 1 :
In device management / Sound Video and Game Controller I deleted the High Definition Audio
Inject a driver from softpedia,
http://drivers.softpedia.com/progDownload/IDT-High-Definition-Audio-Driver-61064290-for-Windows-8-x64-Download-188054.html

Option 2:
In device management / Sound Video and Game Controller I deleted the High Definition Audio and try the installation of HP.

All is good.