It is very possible that the camera is still set to default settings, which would mean it is in PSMI mode, not MAS mode, meaning, the computer treats it as a device, and not a a USB mass storage device (as in a card reader) which I am assuming you are trying to accomplish.
To remedy this, you need to go into your settings, under menu, and look for the setting called “USB.” You’ll have two options, Chose “Mass Storage.”
Now, this may not fix your problem, it could be anything else, too.