So I'm on an Acer 471G V3 as the person who asked the question is, and the microphone isn't dead totally, but you set the levels to maximum with a maximum boost and you just barely get any indication that it's hearing something, if you blow directly on it (1/2 way left of the webcam).
When you use window's 7's "set up a microphone" wizard, the part where it asks you to read a sentence will show you're constantly in the yellow area of levels before the green, and never approaching red. It always concludes that "the computer did not hear anything, please ensure that your microphone is not muted..." etc. If you blow hard on there you can get the level to cross to red (assuming you maxed out the level to 100 and put the boost to max +48db) and it will say your microphone is working normally. It is not working normally though, the built-in mic is, simply put terrible.