Megavideo Sound My Sound And Speakers Work Everywhere EXCEPT For YOUTUBE. And No, My Volume Is On Its Max.?

My sound and speakers work everywhere EXCEPT for YOUTUBE. And no, my volume is on its max.? - megavideo sound

My sound works fine in Media Player, Putfile, YouTube, Dailymotion and YouTube, but no. I see the video but no sound. I checked the volume on YouTube and has already reached its maximum. I really do not understand what happened.