I only have this problem with 7, so I know it is not a hardware related issue. I simply can not get any sound out of my graphics card (seemingly) through HDMI.
I have my bios setup to play audio from it. I've followed what everyone else has done when using the search, I have zero success. It worked before using 7, so I am 100% confident that this is a 7 issue (because it still works on Ubuntu!).
All drivers and software is up to date too.
Mobo: M3a79T Deluxe
CPU: Phenom II X6 1090T
GFX: GTX 275
I am ready to pull my hair out.
I want to reinforce... it works on my Ubuntu install!