Umm.. That's a tough one. You could try downloading the firmware from the sandisk website for that particular flash drive. There is also a way to format that USB drive using conhost. Just type in conhost in the start menu. Look this up online and try that. It's like the ultimate way to format your hard drive. You can also try going into computer management and formatting in there using the on screen instructions. That's about all I can recommend. If you do all of that I'm confident you'll be back to factory.