And if what Hakumi said doesn't work, right-click the file and go to Properties, and then a little window should pop up showing you the properties of the file such as what kind of file it is. Right there in the first tab it opens on should be an option that says "Open With..." and from there you can set what program you choose to be that kind of file's default program. Once you've chosen, click either the Apply or the OK button on the Properties window and it should work. Unable to get on my computer right now so it's hard to explain this without visually looking at it, but I'm sure someone else can explain this process better than I did if you're confused.