Windows 7 - Microphone problem

Hello , I'm simasce and this is my first post

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1 month ago I've got a big and annoying microphone problem
I've started a VoIP game and when i talk users hear a weird sound like scratches and when game gaves some sound then they hear it
On skype users doesn't hear anything

I've searching for help because this problem has got on my nerves!!!
I've tried the update - no works

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Look's like i found the problem: microphone records computer sounds (does the stereo mix job) , but can someone help me how to remove THAT???

One weird image that my Windows 7 shows

Yes - Right click on stereo mix and select enable it then right click again and select make it default.
Or if you just want the microphone disabled Right click on it and select disable.

Thanks so much!
I've disabled and enabled my mic and did the same with stereo mix , but disabled it and...VOILA!
Thanks!!!!!!!