Use DiskPart Open a command prompt window for the windows version you are using

• In the command prompt type diskpart
• Type list volume to identify the thumb drives volume #.
• Type select volume # where # is your thumb drives # and press enter.
• Type attributes disk clear readonly press enter. You should get text back saying Disk attributes cleared successfully

Remove the flash drive, then reinsert into USB.
Check the drive in question, you should now be able to access the disk with full permissions.