My macbook (not the new edition)'s trackpad button started to make a weird noise all of a sudden. When I click, it feels like something's breaking inside. I don't know what happened. Any idea?

Answer:
Most likely it's the epoxy that holds the underside of the button to the top case degrading or the plastic has cracked in the button mounts. It most likely will be fine for a while as long as it still works and you're not too hard on it, but eventually you should take it in to be repaired. If it's still under warranty Apple will fix it for free, if not it depends on what part is broken.

EDIT:

The firmware update only works for the 'new edition' MacBooks, it's not relevant to yours. Besides, if it's making a noise that's not coming from the speakers then it's a physical hardware problem.

Answer:
Apple just put out a firmware update for the new MacBooks on their site. It should also be available via software update. if that doesn't fix it - take it into Apple and get them to check it.

It maybe a hardware problem. Download the firmware update and try it first. If that doesn't fix it then take it into Apple.

Back up any stuff you’ve on your laptop first.