Ohh, well then it's definitely file protection. It's probably still marked as 'in use' or reserved by a process. Or still also possible, a hardware error.
Reboot in safe mode, change current user account settings to 'never notify', type in services.msc in your search field, go to administrative tools > services > protected storage. Turn it off.
While you are doing this stay off the web, you are running windows with its immune system off.