A file could be unremovable for a number of reasons.
- A process has a file opened with exclusive access
- You don't have proper access to the file
- The USB drive has a physical 'read-only' switch
- The USB is mounted as 'read-only'
For the first item, you can use a tool such as procexp to locate any handles to the file in question and kill the process
For number two you would need to right-click the file > properties and look in the security tab to verify you have sufficient privileges to the file to delete it.
In the third bullet, you would inspect the device itself and verify if it has a switch, if so make sure it is not in the write-protect toggle
For the last item, you can use use the built-in diskpart utility to confirm the USB disk and volume are not 'read-only'
Diskpart:
To launch, simply type
diskpart at a command or Powershell prompt
list disk will show you available disks
list vol will show you available volumes
You will need to select the correct disk (this will be apparent by the size) which one is the USB then type
select disk # and
select vol # (should be identifiable by the LTR assigned
Run the commands
detail disk and
detail vol and look at the read-only attributes to confirm they say no