Like everybody I often have to search to what program an extension belongs.
I found a very helpfull website that supports you in solving the questions.

File extension is a set of characters after the dot in the name of a file. A file named "FileName.doc", for example, has "doc" as its file extension.

Extension.informer.com is a database of file extensions and various programs that utilize them. All the information is gathered from the users' PCs through Software Informer Client.

Just enter the desired extension in the "Search extension" box and push the "Find" button - and you will come up with a list of programs this extension can be associated with. The top program in the list will be the one that is used with this extension by the greater number of the Software Informer users. You may choose any program in the list and visit its page on software.informer.com with a single click. There, you will be able to download this program and look through its review.

http://extension.informer.com/

Just go to the website, search up the extension and you will be able to download several programs and/or tools that support that extension