The new XML-based format in Office 2007, Office Open XML, is now an official ECMA (European Computer Manufacturers Association) standard. We have put a lot of effort to make this happen and ECMA will also take this one step further and submit it to become an ISO standard which is great news!
If you want to read the words from ECMA, have a look here.
If you are not using Office 2007, which you probably aren’t since it just been released, you can still use the new format with your old Office version. If you are using Office 2000, XP or 2003 you can download a compatibility pack and then you can read files saved in the now format and you can also save you own files in the new format. You find the compatibility pack here.
The new file extensions will be .docx, .pptx and .xlsx
This is very good news!