Can't find a valid editor for this file extension

Question

I've changed Extensions.txt in

Program Files (x86)\Adobe\Adobe Dreamweaver CS5.5\Configuration

And I've changed MMDocumentTypes.xml in

Program Files (x86)\Adobe\Adobe Dreamweaver CS5.5\Configuration\Document Types

But I'm still getting "Can't find a valid editor for this file extension".

Answer 1

 in dreamwaver just go to
 Edit > Preferences > File Types/Editors
 you will find .js .asa .css .inc .txt .as .asc .asr .htaccess .htpasswd
 add your extension at the end to be like this
 .js .asa .css .inc .txt .as .asc .asr .htaccess .htpasswd .lng
 my additional extension here was .lng file.
 it really saved me a lot of time.thanks