Word 97, 2000, 2002, and 2003 all use the same file format. With the
exception that certain new features introduced in each version will degrade
in earlier version, files can be exchanged freely among those versions. Each
newer version can open files in older versions (all the way back to Word
2.0, I know, and probably 1.0). Each version also has a provision for
creating files that don't use features introduced in versions newer than a
specified one; for example, in Word 2003 (Tools | Options | Save), you can
select "Disable features introduced after" Word 97 or Word 6.0/95.
Word 2007 uses a new file format. It can still open files from older
versions, but older versions need a converter to open files created in Word
2007 unless they have been specifically saved in the older file format.
