frecklefoo To be clear, with ALL sound from your computer muted, at the computer level, you still get the buzz when you're playing? And this is true no matter what sound device you currently have connected, or if you have none connected at all?
Can you describe the buzzing noise a bit? An audio recording (like from your phone) would be great, but if you can't manage that, at least some idea would help.
Please also provide a dxdiag. Click Windows key-R, enter dxdiag in the run box, wait for the scan to finish, click "Save all information," and save the file to your desktop. From there, you can attach it to a reply using the paper clip (Attachment) icon included with the other formatting buttons.