What's the point of audio coming out from the Graphics,and where does the graphics card get to decode the audio?

I have the HD3870 card,how can I make use of the audio capabilities it provides?

As far as I know, you can only get audio via HDMI. The drivers for it should be installed when you install the video card drivers. Should be as simple as connecting the DVI-HDMI adapter and the HDMI cable to your computer and monitor/TV.

I'm running my 3870 this way to a 42" LG LCD, works beautifully

You may run into some issues on the way though, no sound and the such. If you have problems with the sound, read this:

http://www.tomshardware.com/forum/ [...] adeon-3870

On an alternate note, if you're on vista, to make sure the sound is working, go "Control Panel" --> "Sound", and check which devices are working. You'll want the HDMI as your default, and that it is labeled as working. If you don't see it, right click in that window, and make sure "Show Disabled Devices" is checked off, as it might be hidden. Beyond that, you might have to go searching the net for the RealTek driver. I'm not sure where to look for that, but I'm sure other people do.

Well so far I'm not using hdmi cable nor do i plan to use on the near future.Was just wondering what the deal was.

So it's just for devices with hdmi input.

Are the audio drivers included with catalyst?Cause i seem to have problem selecting the ati hd sound on control panel,I get an error of "device not functioning properly, drivers not found (error 38)"