BlueRevolution said:
so what's the difference between mic in and line in?
Basically, because your microphone is a purely passive sound collector, it generates a very low voltage signal. The voltage level / strength of that signal is a lot weaker than the signals that are carried, by standard practice, in audio lines. That standard signal strength is called "line level" -- it's the level that, for instance, a TV expects from a VCR, or your home theater receiver expects from a DVD player, and so on.
Line level, the standard level, is a higher voltage level than a passive microphone will generate by itself. So a pre-amp would boost it up to that level (it's called a pre-amp because there's an amplifier that boosts from line level to the power output that speakers would need, which again is much more than line level).
You *could* also try turning the gain all the way up in the preferences, to compensate somewhat for the weak signal, but it may not be enough to compensate.
What is the microphone for? Is it for AV chat or gaming? You might consider a bluetooth headset instead. They've gotten a lot cheaper, you get around this problem, and they're wireless.