Microsoft Word, for example, now saves to a .docx extension instead of .doc
Unfortunately you cannot open Office 2007 files from Office 2003 or before.
While you may be months away from considering the upgrade, your clients and friends may have already done so – you may not be able to open their Word or Excel files. The good news is that we have a patch that we can apply to your computer that will convert this new format so that you can open these files. Feel free to ask us to install it to your computer.
by Mike Shinn