When you click open you do you get that small window that says "Search the web for the correct opening program" and "Choose a list of installed programs"? If you do then click the option "Choose a list of installed programs", it should be the second option.
EDIT:
Here, do you get a message like this:

If you do then select the option circled in red and the program Notepad should show:

Otherwise you may have to click that "Browse" button.