I'm sorry about the issue. Was it working fine previously? Or is this a new Canon camera or new computer?
What happens when you turn on the camera and connect it to the computer with the camera's USB cable? Does it show in Start -> Computer on the computer? Does it show anything different on the camera's screen?
Can we do a remote support session, so I can troubleshoot the issue directly on your computer together with you?Please reply at the box below. Thank you,