One USB flash drive I have somehow got corrupted a while back to the point that there was nothing I could do with it: it kept presenting me an error message saying it had been write-protected, but I never applied write-protection to it or anything . . . basically, it rendered the drive useless: I could delete files I no longer wanted, or edit/rename files I needed to, and whatever files I moved or copied to it . . . well, some of those files would disappear altogether, or they'd be inaccessible. I eventually learned it may have been because this particular flash drive was a FAT32 file system, which apparently is not very reliable, secure, or stable as an NTFS system - that would explain why I haven't had any problems with any other external drives I have.
I did every single method the internet had to offer to try and fix it: registry edit, Command Prompt edit, virus scan, properties change, formatting, even trying to restore factory settings, and nothing worked.
So, all this leaves me to do is destroy this and go out and buy another new flash drive . . . when I actually have extra money to spend on such a frivolity.
At least this wasn't a drive that I kept anything important on, but even so, I have a separate USB flash drive, plus an external hard drive for those things.