HOWTO: Identifying and Changing Default File Type / Program Associations
If you need to identify which program opens a particular file type, you can do that, and a lot more, using the Folder Options functions in Windows Explorer.
To find Folder Options, open Windows Explorer (right-click on Start, select Explore). Then, on its menu bar, select Tools and then Folder Options…

At this point, we need to select the File Types tab.
On the File Types tab, we see a large, scrollable box that lists file types. As we scroll down the list, we see various file extensions (such as JPG and DOC) along with a text description of the file type.
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