Creative Element Power Tools is a collection of productivity tools for Microsoft Windows Vista, Windows XP, Windows Server 2003, Windows 2000, and Windows Me. One of the file utility is File Type Doctor which allows user right-click any file and select Edit File Type to modify the applications used to open files of that type. Use File Type Doctor to choose default programs, add or remove file types from Explorer’s New menu, and customize files’ context menus.
More utilities here: Windows Vista File Associations Advanced Editing Management Tools