Primary HDMI and secondary HDMI
As someone who has dealt with htpc, laptops, and hdmi configurations I know a few things about setting stuff up.
On the PC side.
Make sure all drivers are up to date. Including a audio over hdmi driver for xp and older cards. Make sure your graphics card supports audio over hdmi to begin with. Is the sound muted and turned up? Obvious. Cables tight? Obvious. Is the audio playback device set to hdmi or SPDIF under system sounds. Obvious
TV and Receiver side
On some models of these devices there is something called a PRIMARY HDMI. Now for most of us we think we can just plug an old HDMI cable into any ol hdmi port and expect audio. WRONG! You need to use the primary HDMI. On my receiver I use hdmi 1 on my grand parents Sony Brivia (older model) I have to use HDMI 2. so try different ports and read your user manual. They tend to tell us stuff about HDMI we tend to skim over it. I don't know if the newer TV and receivers have this issue or not but try it out.
As far as settings make sure it's set to the right hdmi port and that the audio is set to it. Make sure the sound is not muted and turned up. Obvious. You may also need to turn your tv on and off for it ti sync up with your video card
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