Muvee comes up automatically every time I plug my iPhone into my computer.

At some point, I accidentally chose a program, Muvee, to open automatically every time I connect my iPhone to the USB port. This is frustrating and often slows my computer and I'd like to change this default setting, but I don't know how, nor can I quite figure out what to Google to work out how to change it. Can anyone here help?
Thanks,