If you only download the pictures from camera, you need to change the setting of the camera communicates with the computer. It's reall easy:
1) On the camera, push the "MENU" button
2) Toggle over to the second set of tools (the last one on the right)
3) Toggle down to "communication" and change it from "normal" to "PTP"
You can download the ZoomBrowser from canon websitehttp://usa.canon.com/cusa/support/professional/professional_cameras/softwareapp/zoombrowser#DriversAndSoftware