Speakers caused major damage to my notebook?

I recently bought an external speaker from CD-R King. Once plugged in my Asus K42F, a weird sound was produced by my Altec Lansing built-in speaker. After which, Altec Lansing's Left speaker isn't working anymore, while the Right speaker have worst quality ever. I need help with this. I plugged in a headset, quality's good. When I unplugged it, the built-in speaker sounds like trash. Help everyone.