No desktop PC sound on TX-NR717

I'm using a TX-NR717, and outputting audio from my Windows 7 PC over the HDMI on my Geforce GTX 570. Sound is great, though when I am on the desktop, the receiver says "no signal". If I play a song or something, I miss the first few seconds as the receiver takes a moment to switch to "multich" from "no signal". When using the desktop, all the little clicks etc are not heard. Whenever I click something that should make a quick sound, the receiver starts to switch modes. By the time it can, the sound is over, so nothing is heard, and it goes back to "no signal".

Is there any way around this, where I could keep a constant signal from the PC, or have the receiver already in the right mode before the sound happens? I can't figure out a way to keep it from reverting to "no signal" after every sound.

I should note that when a song is already playing, Windows mixes the click sounds and stuff in just fine. It is just like it outputs nothing on the audio when there is no sound, and when it decides to make a sound, my receiver doesn't realize it soon enough. I don't have this issue if just running HDMI directly to my TV's stereo speakers.

Found a workaround for this. Don't know whether it is my video card's fault for not outputting constant audio (it works with my TV), or the receiver's fault for not switching modes instantly. Anyways, I still have my sound card in my PC although I'm not using it, so I set it the line-in on that card as the primary input device, and turned it on. I keep nothing actually plugged into it, and its volume set to 0, but this causes a constant audio output, which solved the issue.