There is some variable within having my HTPC plugged in and connected to my other equipment that causes noise!
I use my HDTV as the audio receiver and output that to computer speakers. It's ghetto - I know - but a dedicated audio receiver is the next thing on my list. Without the PC in the equation, things work fine.
However, as soon as I plug ANYTHING from the PC into the system, even component video, there is noise in the audio. Even with the PC plugged into the wall but powered down I get this problem. Unplug the PC and all is well. Plug it back in and I hear the buzz again (it sounds like when an RCA plug is touching your finger and connected, though a bit quieter).
The PC must be physically plugged in for this to happen. Even when connected to a switched off powerstrip, it makes the noise. Unplug the strip and everything is fine. The PC will send out the noise with nothing plugged into it (no monitor, USB) except a headphone cable, and/OR the component cord from the MyHD card (with the other one of the two disconnected).
The noise is a factor even when the TV is off or switched to another input.
Please help me to end this curse. I think it's also affecting picture quality via component, as the same 25 foot cable works PERFECTLY when connected to a DVD player in the other room, but I get noise in the picture through the HTPC (the other option is I need a higher quality VGA->component adapter, but the audio is still a problem).