Audio problems: Can't play any audio off internet. Speakers work, can't hear any video or music on internet.?

I just got a new HP laptop that runs Windows 7. I'm used to Vista, however problematic, and I've never had this problem before. My speakers work when I'm playing music from my library, but whenever I try to watch something on the internet, I get nothing. Youtube and some other sites, I can't hear anything. I've checked all the volume controls on my computer and the video file I'm watching and I can't find anything obvious. Is there something wrong with my computer? It's just on the internet. I can't hear anything off the internet. So far everything else seems to be working.