Once complete (showing 100%), close the tool. Open Windows Disk Management (diskmgmt.msc). Windows will prompt you to initialize the disk. Select MBR or GPT, then create a new simple volume. Finally, perform a normal Quick Format (exFAT or NTFS).
If your USB drive is reporting a capacity of 8MB or refusing every format command from Windows, a low-level format is your final hope. Just remember: patience is required (hours of waiting), and certainty is critical (one wrong click). usb lowlevel format
Deep-seated boot sector viruses can sometimes survive a standard format. Once complete (showing 100%), close the tool