After using Skype for months suddenly I can't get my microphone to
work. I am pretty sure all Windows settings are OK. I activated the
microphone in Windows audio record settings, adjusted the volume, etc.

When I try the microphone test in the Windows Settings (Sounds and
Audio - Voice - Hardwaretest) it detects my microphone but doesn't
pick up my voice. This microphone works on another PC. Also I tried a
different microphone (both USB and regular one), still doesn't work.
But, my notebook built in microphone works.

Does anyone have an idea? I will pay a tip of 5$ for the correct answer.

Sounds like the line-in plug may have died? Not unheard of. Does your
sound card have separate line-in and microphone jacks? You could try
the other, if it does. If it is indeed dead it will be cheapest to buy
a PCMCIA or USB sound card to replace yours, assuming your laptop is
outside of warranty.

One of the microphones which I tested is connected with USB. Do you
think it could still be a broken line-in plug on the notebook?