Microsoft Office 2007 new XML format has created many frustrations for people trying to open files created in the new file format on older office suites. Microsoft created an office compatibility pack to fix this problem, and is recommended that you install the pack if you are using an older office suite than office 2007. If you only need to view a file in the new .XML format, then you can install a Firefox plugin to do that. the plugin is called OpenXML and it can be downloaded from here save it to your desktop.
Extract the zip file to your local folder.
The zip file contains the Readme.txt, the License.txt file and the Firefox extension installer OpenXMLViewer _ win _ firefox.xpi.
click on the .xpi file. The codesigned plugin information is displayed on the screen, signed against MindTree Limited.
click on Install Now.
Once the plugin is installed, restart Firefox.
Once Firefox is restarted, navigate to Tools>Add-Ons. In the extensions tab, OpenXMLViewer should be visible.
