No sound in any media player

No media player has any sound. If I try to play any video file there is only video, and no sound. This happens with Windows Media Player and Media Player Classic. I have K Lite Codec Pack version 8 Installed.

When I open Dxdiag it shows the error

Error: Problem getting extra sound info, result code = 0x80004005(Generic Failure)

From the Sound Properties, if I try to open Advance Setting I get the message

DirectSound Setting not available

I can listen system sounds only not media player sound. Why? There is not drivers errors as I can listen sound when I watch videos on youtube.com.

This looks like either a driver issue or a DirectX issue. I'd recommend completely uninstalling the sound drivers, then updating them with the newest version available for your hardware, and grabbing a copy of the latest dxredist from Microsoft and installing that as well.

Just because you can play sound through Flash doesn't mean there isn't an issue with the sound driver, as Flash doesn't leverage DirectSound. Make sure to uninstall/reinstall and not just update in place, as that also makes a difference, especially in issue where the old driver is corrupted.