For sure hes got a HD Radeon card running, and has a DVI to HDMI cable with the necessary pins making contact to grab the audio,, if indeed he unplugs his toslink cable and he has sound,, then I believe its comming from the video card,, I got a HTPC that I just completed here with a Radeo4850 hooked up with the DVI to HDMI cable that came from my BEV9242 to my Onkyo and I got sound and image being sent to the TV. Its all good. But yes,, if it were lets say a previous generation ATi card, (non-HD) and hooked up the DVI port to the amp, no sound. DVI as a standalone has no sound.
Panasonic PT-AE4000|Pioneer VSX-1021K|Energy Connoisseur CF-50, CC-10, CB-10, Velodyne VDR-12|Sony BDP-S350|Roku 2 XS|Harmony One
LG 55LE5500|Elite VSX-43|Yamaha NS-8390|Polk Audio PSW-10|Samsung BD-P1600|Roku 2 XS|Harmony Smart Hub
LG 42LC7D|Roku 2 XS|Harmony 600