For those of you with sharp eyes, you may have noticed that the date on the download package for the Office File Format Compatibility Pack was updated to 11/19/2007. This last update of the compatibility pack was actually in June 2007, when v3 was posted (including bug fixes covered in http://support.microsoft.com/kb/936695/en-us). The change to 11/19 occurred due to changes in the OS compatibility matrix on the web page. So, you should check periodically to make sure that you have the most current Office File Format Compatibility Pack, but if you have v3, from June 2007, you’re still OK.
Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats