If you frequently save Word documents in the old file format (.doc files), you can change the settings so that Word saves in that format every time.
Go to File > Options.
Under Save documents, next to Save files in this format, choose Word 97-2003 Document (*.doc).
Important: Formatting and layout that depend on features introduced after Word 2003 will not be available in the .doc file. For more information on possible differences, see Compatibility changes between versions.