Make sure the sound card is set to output in a hz range that your receiver supports, That was the problem i ran into with my receiver, I had the sound card set to 96khz and the receiver only supported up to 48khz so I got no sound.
The setting should be in the Playback device properties Advanced Tab under Default Format if your using win7.
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The setting should be in the Playback device properties Advanced Tab under Default Format if your using win7.
I also have realtek, so it's worth a shot.