Having the same problem as you I was very relieved to find this registry edit fix that permanently disables the HD audio controller :
"I have tried to uninstall them in device manager....disable them in device manager yet when I re-boot...TADAAAA there they are again!!
Surely there must be a way to get rid of them?
You can disable them by editing two registry keys.
This value disables the High Definition Audio Controller in the device manager > system devices, it needs to be disabled.
This value disables the High Definition Audio Device/ATI HDMI Audio Device. You don't have to uninstall the devices first and this will also free up an IRQ. After a reboot the devices will show a yellow exclamation point but you can ignore that."
To edit these two values click the start button then type regedit.
Double click HKEY_LOCAL_MACHINE, then SYSTEM, then CurrentControlSet, then services.
Click HdAudAddService, then right click Start under the Name column on the right - click Modify, change the value from 3 to 4 and OK.
Click HDAudBus, then right click Start under the Name column on the right - click Modify, change the value from 3 to 4 and OK.