Hi, It seems I have tried everything, but maybe someone will have ideas: On my laptop with Windows 7 I have Logitech desktop USB microphone nad it produces constant buzz when i am with headphones. If I am without them I get a very strong high-pitched noise which increases, so I guess it's feedback. When I am with headphones, turning off Samsung EDS (Enhanced Digital Sound) feature helps alot, but the buzz is still there. Unmuting mic in playback devices changes buss to hiss. Also it's not a ground-loop because if laptop is unplugged, nothing changes. And the built-in mic works good apart sound quality, so the sound card is okay too I guess? USB mic has no mic boost feature so this is also not the case. I have tried the mic on my roomate's laptop and it acts the same - buzzing and feedbacking. Any ideas? Or perhaps the mic itself is faulty although I think it's unlikely:/ Also, even if my mic is muted or is turned off (has a button for that), it still produces the buzz sound, although considerably more quiet.