When you double-click a file to open it, Windows examines the file name extension. If Windows recognizes the file name extension, it opens the file in the program that is associated with that file name extension, otherwise, it gives you a list of application to you to let you choose the one, which you think is most appropriate for that file type.
Although, you can change the program that is associated with recognized file name extensions, but often users do not find it easy to do. Thankfully, there is a light-weight freeware application, which can do the job pretty easily.
Default Programs Editor (DFE) – An Easy Way to Change File Associations and Much More
DFE is a feature rich freeware application that allows you to edit file type associations in Windows Vista and Seven. It enables you to add, edit, and delete context menu items, edit file type information and change the associated extension for a selected file type. Furthermore, you can also use the program to change Windows Autoplay settings and add, edit or delete autoplay handler programs. Default Programs Editor can be run as standalone program or integrated into the Control Panel applet.
It is a context menu editor, an autoplay editor, and default programs association editor; essentially, the settings in the “Default Programs” Control Panel page. It’s a replacement for the “File Types” dialog in Windows XP, and brings some key features of TweakUI to Windows Vista/7.
And DFE is a portable software and does not require any installation on your computer.