As if I've plugged something into a USB port. When I reopen it it makes the hardware removed sound. This started happening after I updated my Nvidia drivers to the 296.10 version. I updated Windows 7 and such that day too, but as far as I recall it only started making the sounds after I updated the drivers. There was this one weird occasion where I went into the Nvidia control panel when the resolution had changed to 1680x1050 60Hz for some reason and it said I had two monitors plugged in, one called "Analog monitor" or something. When I changed it to use the normal one it disappeared and it hasn't happened again.
I'm guessing it might fix it to wait for a driver update, but what I really want to know is whether anyone else has experienced this problem. It seems rather... unique.