To avoid losing your data or corrupting the storage drive's partition table, always make sure that you have closed any open files and terminate any actions regarding your USB drive (including Windows Explorer), and always use the Safely Remove option before unplugging your drive. The above error happens because when you accidentally – force – unplug (disconnect) your external USB drive (USB HDD, USB drives, etc.) without using the Safely Remove Option (“ Safe Remove Hardware”) option, then the USB drive Partition Table becomes corrupted. As a result of that you cannot access your data using Windows or another OS. Sometimes the following error appears after you have accidentally unplugged your External USB drive without using the Safely Remove option: “ You need to format the disk in drive X before you can use it.