I have a HP EliteBook 8530w with Windows XP, I recently wanted to watch a movie on my VIZIO TV.
For some reason the sound is not transmitting through the HDMI cable to the TV, the picture is great but the only sound is coming out of the laptop.
Oh and this is not a DVD I am trying to watch from an AVI file.
I had the same problem on my HP Elitebook 8350w running Windows 7 Enterprise. In Vista there was an HDMI output. In Windows 7 there is just the default "SoundMAX Integrated Digital HD Audio" speakers and SPDIF Interface. I had to switch the default output sound to SPDIF and it started working. Of course it has to be switched back to Speakers later when I want the sound to come through the laptop speakers.