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A couple of hours ago, I attached (USB) my Nikon DSLR to a newer PC for the first time. The OS (Win Vista on this PC) searched for the driver, downloaded the driver, and instructed me to restart the computer.
After restarting the computer, I was able to download the photos without a hitch.
I normally use my other PC (Win 7) for downloading (transferring) pics from my camera to the PC.
You need to download and install the driver from the manufacturer's website, for your particular camera make and model. Then restart the computer, and connect the camera to the PC.