Hi Laszio,
Welcome to the HP Forums! I see that you are looking for a driver to get your Beats Audio working correctly with 8.1. I have included a link to an 8.1 driver below. When you go to install it make sure that you right click the file and Run as Administrator.
IDT High Definition Audio Driver Windows 8.1:
http://h10025.www1.hp.com/ewfrf/wc/softwareDownloadIndex?cc=us&lc=en&softwareitem=ob-124012-1
Let me know how it goes.
Thank you,