hope this would help..
Run: 'regedit'
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Cl ass\{4D36E96C-E325-11CE-BFC1-08002BE10318}\0001\AD1981\Disable
There are two binary keys in there, "MicV" and "MonR".
Both have 01 values.
Change them to 00 so they won't be disabled anymore.
Restart.
Now you can go to Speakers in "Playback devices", hit "Properties", then "Levels", and there you have it: you can Mute/Unmute microphone monitoring and even set a preferred level.

