[color:"orange"] Can you change that to something else? [/color]
No, Realtek HD audio Output is the only option.
It's an onboard-card.

[color:"orange"] The initial description sounded like your microphone was simply much more sensitive than your friend's, but unplugging it eliminates that possibility. [/color]
This was my first thought too, so first thing I tried was disabling my headphone and enabling my speakers, but my friend told me that the volume nor the quality of the sound hadn't changed a bit.

[color:"orange"] Some monitors (and possibly keyboards) have built-in microphones, but they would likely be visible even if they were not labeled. [/color]
My monitor is rather old(almost 10 years IIRC, definetly more then 7 years), I don't see any kind of microphone on my keyboard.

[color:"orange"] If your friend can tell the difference between hitting a key normally and hitting it hard, then the sound is not from a program or accessibility feature. [/color]
Next thing to test.

Another thing that might be usefull: for 'recording sound' and 'recording speech' I can use the following devices: Realtek HD audio Input, Realtek HD Digital Input and 713x BDA Analog Audio Capture. Both Realtek Inputs seem to work, but when I select the Audio Capture, my headphone doesn't work.

Thanks for your help so far.

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