The .ppt file extension is used for Microsoft PowerPoint presentations that were created with versions of PowerPoint prior to 2007, whereas the .pptx file extension is used for PowerPoint 2007 and PowerPoint 2010 presentations. Opening a .ppt or .pptx file is as simple as double clicking on it in Windows Explorer. The presentation will then open for you to edit in PowerPoint.
But what if you don’t have PowePoint installed on your computer?
Fear not! For all the people who don’t have PowerPoint, Microsoft have made available a utility that is free to download: PowerPoint Viewer.
Although PowerPoint Viewer doesn’t let you change an existing presentation, it will allow you to view it.