Your PC will send the audio to one sound card. Your choice will be the (4850 built in sound chip->REALTEK) or your motherboard audio card(built in or PCI/PCIE base card).
You can select where to send your audio on CONTROL PANEL->AUDIO option. The playback choices will be HDMI or the other audio card(i.e. speakers).
I'm not aware of any work around. The PC audio only goes to one playback hardware.
To site you an example i have 4890(w/ HDMI on 2 HD Monitors) with Creative XFI soundcard. I use the CONTROL PANEL to select which playback hardware i want to use. If select the HDMI the audio goes to the designated primary monitor/display. If i select speaker the sound goes to the XFI card.