Earlier we had seen how to set keynote as the default application for opening a PowerPoint presentation file. In this tutorial, we will be seeing an alternate way by changing the file association on Mac OS X Lion.
Launch Finder application on Mac System and and locate a file for which the association needs to changed. Then right click on the file and select Get Info from the menu list.
In the Info window, navigate to Open with section and select your Preferred application
If you want to keep this association permanently and use this application to open all documents with this file extension then click the Change All button.
You will be prompted with the following warning message. Click the Continue button to apply this change to all documents with extension “.ppt”.