Audio problem after upgrading video card

Hello,
I have an HP Media Center PC m7350n computer running Windows Vista Ultimate 32-bit with (I think) an audio driver issue. The problem occurred after I upgraded my video card to an ATI Radeon HD 4850 with HDMI, DVI, and VGA output. The audio cable is also being plugged into the monitor, which has built in speakers. If I plug in the computer via HDMI, everything works fine, but I would like it to be connected via DVI and not HDMI.
When I plug it in via DVI with the separate audio cable, I get no audio. The audio icon in the bottom right corner has the dreaded red X and it says "No Audio Output Device is installed." When I right-click and go to playback devices, only "ATI HDMI Output" is listed which is not plugged in.
I have downloaded the Realtek driver from their website and installed it and it seemed to to absolutely nothing. In the Add/Remove Programs, I have Realtek High Definition Audio Driver ... but it still not working. I have no idea what to try to fix this problem. Any suggestions would be greatly appreciated!

Thanks,
Matt :confused

 

I'm not an ATI aficionado, but I believe there's a setting somewhere in the ATI Catalyst Control Center where the 'ATI HDMI Audio Output' can be changed or disabled. Other than that, I'm not really sure why the ATI is over-riding the on-board RealTek audio..... hopefully someone with more ATI knowledge will come along, but until then, I'll try to do some more research and see if I find anything.....

oh yeah.... :wave Welcome to Major Geeks! :major