Office 2007 Compatibilty Issues

The most recent version of Microsoft Office, Office 2007 has introduced new file formats which cannot be opened in previous versions of Office without the installation of an extra piece of software. This means if you create files in Word 2007, Powerpoint 2007 or Excel 2007, those files may not be readable by others unless they have installed the necessary piece of software on their computer. These new file formats are identified by an "x" at the end of the filename extension e.g. .docx is a Word 2007 file, .xlsx is an Excel 2007 workbook and .pptx is a Powerpoint 2007 file.

If both parties have Office 2007, the files can be opened. The downloaded files change to .zip files instead of .docx (or .xlsx, .pptx, etc). Once downloaded, the files can be simply renamed to the appropriate extension and they will work properly.

If you cannot be sure that the person you are sharing your document with will be able to open an Office 2007 file we would strongly recommend that you use the "Save As..." functionality in the particular Office application and choose the appropriate type to save as. e.g. in Word 2007, you can select "File > Save As..." and then select the "Word 97 - 2003 (*.doc)" option in the "Save as type" drop down menu. This will save your document in a format that can be opened by people using older versions of Office.

More information on the new Office file formats and information on how to share these files with others can be found on the Microsoft web site.
http://office.microsoft.com/en-us/help/HA100069351033.aspx