What is wrong with my MacBook?

Today, my mac freaked out on me twice. I was watching something via Quicktime and all of the sudden the screen went black and green and started going crazy like it was twitching or something. And I got this loud noise coming out of my speakers. My MacBook is about 3-4 years old. Does that have anything to do with what happened?

 

Once that happens, I unplug my speakers right away, because it's a very loud noise. I wouldn't be able to restart the application because the screen goes all twitchy on me. When it first happened, I tried pressing some of the keys and nothing works. When this happens, my keys and everything are all unresponsive. I can only restart from the power button. I downloaded a different file of what I was watching and it was fine up until a few minutes ago. I really wonder if it's my computer.