Sound help needed

Hi there im having a problem with the sound on my laptop and was wondering if anyone could help... i am able to download movie files and watch them and can hear the sound and watch movies with sound on some websites but i am unable to hear the sound on myspace or youtube video files and a number of web sites



Anyone help please?????

Do you have flash installed? What operating system are you running? In vista, you can mute the audio from a specific program, so check your sound settings to see if you have accidentally muted your browser or something if you are using Vista.