I've looked at the Device Manager. Under the USB Controllers link I have two separate USB Mass Storage Devices listed, one of which has a yellow exclamation mark against it. The properties for this show "Windows cannot use this hardware device because it has been prepared for "safe removal", but it has not been removed from the computer. (Code 47)".
I've tried uninstalling and reinstalling drivers. When I try to update the drivers I get a message that the wizard can't find a better match than the drivers I have.
I'd appreciate advice on how I can fix this problem.