here it all is again
click on My Computer icon,
From the menu select Tools,
slide down to Folder options, click
From this sub window select the File Types tab,
find and select the file type you're interested in and highlight it
click on the Advanced tab
in this sub window, you should see a number of actions (NB they're not always all there) the common ones are RUN, OPEN, EDIT, VIEW.
Highlight the action you wish to change, then hit the Edit button.
Make the changes you want.
Exit hitting the Apply, Save, and OK buttons, whenever they appear.
NB Change every action you may use with this file type, as you can have different actions open different programs. I once had a system set to VIEW images with ACDSee, while OPEN activated Photo Shop.
If you change all the action, this should promulgate through the system. Usually doesn't require a reset, but sometime it does. It's MS Windows, what more can I say.