Here are main presentation formats supported: Microsoft's explanation of the benefits of the change included: smaller file sizes, up to 75% smaller than comparable binary documents security, through being able to identify and exclude executable macros and personal data less chance to be corrupted than binary formats and easier interoperability for exchanging data among Microsoft and other business applications, all while maintaining backward compatibility. The big change in PowerPoint 2007 was that the stable binary file format of 97-2003 (.ppt files) was replaced as the default by a new zipped XML-based Office Open XML format (.pptx files). Under the General tab, towards the bottom you will see 'Unblock' button or checkbox next to 'Security: This file came from another computer and might be blocked to help protect this computer'. To unblock a file on Windows, right click on the file and open 'Properties'.
Please note you may need to unblock the PowerPoint files downloaded if your Microsoft PowerPoint software can't open them.
