Be very careful doing this.
But sometimes there are files on a flash drive that cannot be deleted with root access. Here is how you get it for the Ubuntu file manager.
1) Open Ubuntu Nautilus File Manager as root.
2) Open command terminal. (Hint: Ctrl+Alt+T)
3) Copy and paste the following (right click copy, then right click paste):
4) Hit enter. The Nautilus File Manager will open with root access.
5) When your done, just close the Nautilus File Manager.