Hi,
Go into your Control Panel, then click on Sound and Audio Devices.
This will bring up the properties for your sound and audio devices, then
click on the Advanced button under your Device Volume section.
Now the Volume Control window will open up, make sure the Advanced options
is enabled, to do this, click on Options, then select Advanced Controls.
Now see if you have anything called Stereo Max or something to that sort and
try muting that, and if you find it, see if there's an advanced button
underneath that section and see if you can disable the echo.