This policy setting controls whether Word 2007 users can open Open XML files saved with pre-release versions of Word 2007.
If you enable this policy setting, Word 2007 users will not be able to open Open XML files created in pre-release versions of Word 2007.
If you disable or do not configure this policy setting, Word 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 Microsoft Office Word 2007. Word Open XML files usually have the following extensions:
Note - See Plan block file format settings in the 2007 Office system (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. Also, see the "File Block Technology" section in Chapter 4 of the 2007 Microsoft Office Security Guide for information about the Microsoft Office Isolated Conversion Environment (MOICE), which provides another method.