I'm sorry for not giving the detailed instructions.
1) if on the internal memory there is only system but no config in system just create an empty folder called config.
2) open notepad and copy, paste the line mentioned above and save it as extensions.cfg on the system/config folder
This is not a hack! No poterm or other funny stuff. This is a completly independent application for your pocketbook. Keep me updated how you're getting on and don't hesitate if something still does not make sense.