It’s easy to save a 2007 file into the 2003 version. (Example shown in Microsoft Word, but it works the same in all Office applications.)
Follow these steps:
Click the Windows logo in the top right corner
Select “Save As” from the list
Select “Word 97-2003” from the list
Choose the location where you’d like to save the file, and give it a name (as you normally would).
You’re done! Your file is now the “old” version which can be opened by someone with any version between Office 97 and Office 2003.
How to Convert Office 2007 Files Automatically
Another option is to download and install a free tool that will automatically convert Office 2007 documents to the old version for you (when you open them).
To convert Office 2007 files for free to a format that you can open, use the link below. The online version of the tool is free, and there's also a desktop version that is available for purchase for $19.95.
This same site offers a variety of other conversion tools, including one to convert a variety of file types into PDF files.
Oconvert Tool - http://oconvert.com/