Just purchased a mac mini duo and it works fine, BUT when I'm ripping a DVD it make a small rattle every now and then, should I take it back to the apple store?
It doesn't sound serious to be honest. Do you have AppleCare? I'd be more inclined to keep using it and see if the problem gets worse or not. So long as the drive is actually working properly it's best to stick with what you've got - if you get the mini replaced there's the chance that the new unit will have less bearable quirks.