reset Settings

Hello,
In Rubymine, i wanted to create a new file, i forget to put the extension so it says something like "there is no extension, what is the default action for this extension?", then i corrected the extension and missclick on the button "associate ...(i don't know what)".
Now, when i double click on this file, it opens TextWrangler :_|
Where do i change this? or where do i reset settings?

I look for "action" or "editor" in the preferences but there is way too many settings.