I am trying to create a startup disk on a USB. I attempted to use the Ubuntu Startup Disk Creator but that failed. I then turned to UNetBootin. That seemingly worked but I still wasn't able to boot from it. Now the USB will not mount to any of my VMs (all linux). I attempted to reformat the usb on my host (Windows) and that didn't work. 

Virtual Box is still recognizing the drive but the Linux OS isn't mounting it. And the Windows reformat keeps failing. Any ideas?

Thanks for any help.