Firstly, in order to fix the issue, update iTunes to the latest version. Navigate to the official web page, click the Download Now button, save the file to your computer and install it following the on-screen instructions. After that, launch iTunes, press Ctrl + O key combination and add again the files you want to transfer in the iTunes library. Next, connect the device to your computer and try to transfer the files. If you can't or if the device is not recognized, right-click the Computer icon, select Manage and open Device Manager. Expand the Universal Serial Bus controllers list, right-click on the driver and select Uninstall. Reboot your computer, connect again the Samsung device and press Scan for hardware changes icon from Device Manager. If you still have issues, I suggest you transfer the files using Samsung PC Studio or Samsung Kies.