Files of the pptm file type are macro-enabled xml based presentation documents made using Microsoft Office PowerPoint 2007 or Microsoft Office Powerpoint 2010. This file type is the default for the newer versions of PowerPoint given that it embeds macros, or user-created scripts that can automate repetitive actions that are taken when creating a presentation. This file type is also much smaller than previous PowerPoint file types because it uses an xml architecture to put together a zip compressed file.
There are several ways to open pptm because it is an open file type. Although the Microsoft Corporation owns the right to the file type, the specifications are open and anybody can use it. Perhaps the best way to open a file of this type is using Open Office 3.0, a free and open source office suite. this office suite comes with a presentation builder that is very similar to Microsoft Office, and has complete compatibility with nearly all Microsoft Office functions. The only problem that one may run into when opening a pptm file in this way is that the macros may not work entirely because the scripting is slightly different between Microsoft Office and Open Office. However, this will not change the formatting or contents of the file.