This policy setting controls whether PowerPoint 2007 users can open Open XML files saved with pre-release versions of PowerPoint 2007.
If you enable this policy setting, PowerPoint 2007 users will not be able to open Open XML files created in pre-release versions of PowerPoint 2007.
If you disable or do not configure this policy setting, PowerPoint 2007 users can open files that were saved in pre-release versions of the new Office Open XML format, which underwent some minor changes prior to the final release of PowerPoint 2007. PowerPoint Open XML files usually have the following extensions:
Note - See Plan block file format settings (http://r.office.microsoft.com/r/rlidGroupPolicyBlockFileForm2?clid=en-us) in the 2007 Office Resource Kit for more information about using Group Policy to manage and enforce file format requirements.