The PPTX file extension represents a presentation file format created with Microsoft PowerPoint 2007, the presentation (or slideshow) application in the Microsoft Office 2007 suite. Traditionally, PowerPoint files were identified by a PPT file extension, but changed to PPTX with PowerPoint 2007.
If you don’t have PowerPoint 2007 installed on your computer and you’re not ready to incur that expense, there is another option available for instant download on the Web that just happens to be free.
OpenOffice is the free, no frills alternative for the common applications in Microsoft Office, the world’s most widely used productivity suite. Just like Microsoft Office, OpenOffice includes an application for word processing (Writer), spreadsheets (Calc), presentations (Impress), graphics (Draw) and databases (Base), comparable to Microsoft Word, Excel, PowePoint, Publisher and Access. The OpenOffice applications will not create the same file format as the Microsoft Office applications but they can open and modify any of the files that were originally created in Microsoft Office.
Impress is OpenOffice’s presentation answer and is compatible with all PPT and PPTX files. It comes along for the ride with the download of Open Office. No separate download is needed. Open Office will run across all major platforms, including Windows, Linux, Sun Solaris and Mac.

