The handbook of PT 2005 contains information about the File Tool listed under the caption Other tools.
Personally, I don't know what's the point of having an icon to the File Tool on the main window but since it was the most requested feature of PT 2005 it was now added.
In PT 2005 you could access the File Tool by using File Finder or File Cleaner, now you can open the File Tool from its own icon and drag files to it.