Megavideo Streaming Services Can't Hear Audio From Streaming Videos?

Can't hear audio from streaming videos? - megavideo streaming services

I have trouble hearing the audio from the video streaming services (Dailymotion, Youtube, DailyMotion, etc..) Whenever I try to watch this video, I could not hear the voice or a part of the dialogue, Background sound score and sound effects.
I am using an HP Slimline PC with Windows Vista Basic, all players have installed and updated website. I've tried to do the same with an old PC and it worked well, running on XP. What seems to be the problem? Thank you!