I'm trying to revive an HP m9300t to use as a HTPC on my TV. I've wiped the HDD and installed Windows 7 Ultimate instead of the default Vista. It has a NVIDIA GeForce 9300 GE with both DVI and HDMI output. (From what I can tell, the card has no sound chip, but it is plugged into the mobo on a spot labeled "PDIF_out2".)
Audio playback devices include Realtek Digital Output, Realtek HDMI Output, and also Speakers & Headphones (not plugged in). The Realtek HDMI Output lights up the green bar on the right when I'm playing a song in media player or watching a video, it looks like it is sending a signal to the TV. Drivers for Realtek and the GPU are up to date, and Bios is up to date too. I've tried all combinations of enabling and disabling the Digital Output and HDMI Outputs. There is no NVIDIA HDMI Output, but I don't know if there should be with this card. No NVIDIA Audio Drivers have been installed. (I tried just for kicks, but it insists there is no hardware on my system that require the drivers.)
The TV (Vizio E420VL) has 3 HDMI inputs. All of them have fully functioning audio with my Xbox 360 and my cable box through all of my HDMI cables, and none of them play sound for my PC.
I originally wiped the HDD because of un-diagnosed blue screens/restarts that we thought was a dying mobo. Before the wipe it wouldn't stay on for 15 minutes, but there have been no such incidents after the Win 7 install.