What to do next when some Word documents will not open after installing Service Pack 3 for Office 2003

After you install Microsoft Office 2003 Service Pack 3 (SP3), you can no longer use Microsoft Office Word 2003 to open or save some files that you could open before you installed SP3. The reason for this is because those files may pose a security risk. All Word documents that were saved using the Word 2.x for Windows file format or older are blocked after you install SP3. See Microsoft Knowledge Base article 941636 "You receive an error message when you try to open a file or to save a file after you install Office 2003 Service Pack 3" for more information.
 
Perhaps you've never used one of the older versions of Word, but still some files cannot be opened after installing SP3. How can this happen?
 
Well, if you didn't create the original file yourself, it is possible that the file has been passed around for a long time and was, in fact, created using the older version of Word. Perhaps the document was created using a newer version of Word and then, for whatever reason, the person who saved the document saved it using an older Word file format. For example, you can choose "Word 2.x for Windows" in the "Save as type" list in the Save As dialog in Word 2000.
 
Another possibility is that the file was created by a third-party program, such as a business reporting program, that generates Word documents using an older Word file format.
 
You can use the FilesBeforeVersion registry entry to override the default file blocking behavior to allow Word 2003 with SP3 installed to open the older file formats. See Microsoft Knowledge Base article 938810 "Information about certain file formats that are blocked after you install Office 2003 Service Pack 3" for more information.
 
However, because the older file formats pose a security risk, you should consider converting the files to newer Word file formats.
 
You can use Word 2003 itself (while using the FilesBeforeVersion registry entry to override the default file blocking behavior) and the Save As dialog to individually save the files using a newer Word file format.
 
It is also possible to use batch conversion tools to convert multiple files to file formats that are not blocked by Office 2003 SP3.
 
The batch conversion wizard in Word 2003 can be used to convert older Word files to the latest Word 97-2003 Document (*.doc) file format. See Microsoft Knowledge Base article 826174 "How to convert many documents to Word format automatically in Word 2003" for more information.
 
The Office File Converter, a component of the Microsoft Office Migration Planning Manager, can be used to convert batches of Office files to the Office 2007 file formats. See the Microsoft TechNet article entitled Introduction to OMPM for more information.
 
For maximum compatibility moving forward, consider using the Office File Converter to convert batches of Office files to the Office 2007 file formats and then install the Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats to open and work with the files using Word 2003.