OpenExpert

Windows operating system creates associations between a given file extension and an application that uses it.

This way, the system knows what program is necessary to open a file. However, the ideal is not a one-to-one relationship because there are many applications that can open the same file type. As an example, let us take an image file: sometimes, you may want to edit it and view others.
OpenExpert will help you create associations between a file type and more than one application. This will allow you to decide what application you want to open a file, instead of using the default program.
OpenExpert’s interface is very easy to use. It is divided into two tabs. What the Extension tab basically does is letting you select those programs you want to associate with a certain extension. The extensions appear on a dropdown list while the programs must be located from the hard disk. Some buttons will allow you to add or remove applications from this file association. In addition, you can set additional parameters for the open-file operation. The second tab will allow you to add applications to a list. You can even add different versions of the same program. As further options, you may make OpenExpert substitute the system´s Open With menu item or export your current configuration to import it later in another computer.
This program has some limitations. First, its help file is not supported by recent Windows versions. Additionally, some Windows 7 users might feel it is not necessary to use OpenExpert because this operating system comes with an improved Open With function, which is much user-friendlier as it shows a list of the programs associated with a given extension and lets you select the default application easily.