Sorry Whiterabbit, I wasn't able to find the function for disabling the mic in thinkpad configuration as well. However, are you sure it didn't help when you mute the microphone in advanced properties at audio settings?
for those who are as dense as I am, you have to select "line in" in the speech control panel settings for it to actually shut the onboard mic off and use line in for a mic.
for those who are as dense as I am, you have to select "line in" in the speech control panel settings for it to actually shut the onboard mic off and use line in for a mic.