Just turned on the pc and microhpone is dead.
@ Dwarf: nothing, basically. I have seen it register noise on the green bar, but not all the time.
@ Maceman: Yes, it is connected via the Audigy 4 pro external unit (Line in 1/mic) with a mini jack. As I have two of the same headset, I tried to switch but there was no difference; still didn't work.
However, this time I have one extra report: although Line-in 1/mic is standard unit, Windows said that Line-in 2 was ready for use, and the green bar was on this unit rather than line-in1 where it should be. As I wrote this, my microphone suddenly worked again, but with the annoying waves of echoing crackles when I speak.
It's almost as if I open Sound setting once and try the different options, nothing changes. But if I close settings, go for a quick walk around the house and open Sound settings again, my changes will work (for removing the crackles).