Originally posted by BigMackCam A quick search via Google tells me that the D3100 can't be used with an external microphone (even using the USB port)...
EDIT: And a second quick search tells me that the Canon EOS550D external mic input is jack only... So a USB microphone isn't going to be any use to you, I'm afraid.
Well is there any software for a computer to connect the microphone and the camera? So I can record from the camera's video/image output and use the microphone at the same time without delay?