Hi there!
There is my problem: I tryed to record my voice via microphone when i am in game (STALKER: Call of Prypat) - and I have sound from game on record. Yes, I am using headphones. Its not over - I turn on music in Windows Media Player and record voice - same problem. There is voice from system in my record.
What can I do?
Select your microphone as your [u]Recording Device[/u]. (Don’t select Stereo Mix or WASAPI Loopback.)
Yup - I done this before 
And it’s still not working? If you are using a laptop, that might be the microphone built-into your laptop and you might have to select a different microphone. If you’re using a USB headset, it should say “USB-something”.