when i disconnet internet that sound disapper.I have checked internet connection,device manager.There isnt any problem.I have scan and fix registry too.

Hi, Please update the driver of sound card and Internet Adapter to the latest version. If the issue persists, please boot the computer in Clean Boot Mode to see whether a 3rd party application cause this. http://support.microsoft.com/kb/929135 Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.