Currently Being ModeratedOct 22, 2012 6:52 PM (in response to Chris in Cary)
If you right-click on a jpeg, choose "Get Info," you will see the option "Open With."
Change the result in the pull down menu to the desired application, then click on the "Change All" button.
In the future, all jpegs will be opened with your chosen application. You can do this same procedure for all other file types that you would like to change too.