Problem with microphone!

Buy a new one

Plug it into the other mic socket if you have one? Worked for me.

Had problems with my Headset yesterday, it kept disconnecting every few seconds, I found out that i´my USB Drivers were corrupt, so I uninstalled them......well, my mouse and keyboard were useless after that ^^ so I had to dig out my old PS2 keyboard from the basement and used my keyboard as a mouse and reinstalled them xD

To your question, if you use Realtek, take a look there, a friend of mine had the same problem, but I don't know exactly how to do that anymore.

Ckeck if your Stereo Mix is switched off, that might be the cause (in Audio Devices)

Well, disable stereo mix, and set your microphone port to both default device and default communications device.

Don't forget to change the settings for voice in both Steam settings and in game settings.

In the mic settings, if the box "listen to this device" is checked, disable it.

Additionally, find the "when windows detects incoming communications, do what" tab and change it from "mute sounds" or "reduce volume by 80" to "do nothing".