Navigate to Start > Control Panel > Programs > Default Programs > Set Default Programs, select Notepad from the list and click Choose defaults for this program. Uncheck the document extensions that you don't want to open in Notepad, click Save and restart your computer. If you still have issues, uninstall Free Download Manager, run Glary Utilities to make sure that there are no leftover registry keys in your system and download and install the latest version of the program.
