After reinstalling my HTPC, I came across an ugly problem. Some TV stations could be made about the volume control of Windows will not make it louder and softer. This occurs only at stations on the sound in Dolby Digital transmit. Where was the problem? After a long search I found the solution in the Media Center randomly:
Navigating the settings in the TV audio to the point and set the hook on "Automatic Volume Control". Thus, after a restart of Media Center played TV stations all identical and can be regulated.