Ok my bad I fixed my problem. The sound volume seemed to impact all my numerous media players (wmp, winamp, quicktimé). Seems it has been possibly an ffdshow audio construction or loudspeaker wasn'capital t pluged in correctly.Apologies for áccusing the Silverlight group, appears silverlight forces all the audio through to your OS set up codecs and filter systems.Worth installing the video to disc and attempt enjoying it in Windows Media Participant if you're having issues with the audio as a check to discover if silverlight is your issue. Yes I was getting the exact same issue with Silverlight 4.0.50524.0 on all the mvc tutorial websites under home windows 7.