To start off - I am new to this site. I need help with an issue that I can't find a solution for elsewhere.

I recently bought Snow Leopard for my late 2007 model 13" Macbook (the old white one). I've been running 10.5.8 for so long, and having Snow Leopard come with my Mac Pro I enjoyed it enough to buy it. I did my research and found I'd need to buy it, there was a separate build needed for my Macbook to work properly. I got it and installed today.

I'm having a problem, though. When I turn my Mac on, the startup sound is fine. Though, as soon as I try to watch a video online or play a song, no sound comes out. I've checked my sound settings and they are fine, set to the appropriate settings.

It plays the startup sound, trash sound, the "error" or "cannot complete" sound, and the sound when you remove an item from the dock; for some reason though, it will not play application sounds.

What's my problem here, and how do I fix it?