All those versions use the 2000 format by default.  You don't need to
convert as each can read the 2000 format.  You would just have to be sure
not to use features in a newer version that don't exist in prior versions.

Access 2002 and 2003 use the same file format. There should be no
compatibility problems even if you have set the option to "Save in Access
2002 Format" and "Save in Access 2003 Format". I specifically say "set the
option" because the default for both is that they save in Access 2000 file
format. This is for MDB files.

In my experience MDE files are still version-specific as follows: an MDE
created with Access 2003 will not run under Access 2002, but Access 2002
MDEs have run successfully under Access 2003. (But I am not certain that
_all_ Access 2002 MDEs will run under Access 2003.)

When you save in Access 2000 format, you give up any new features that were
introduced in the later versions. One that I have found particularly useful
is OpenArgs for passing information to a Report opened with the
DoCmd.OpenReport statement. Colleagues who do more data analysis
applications are find Pivot Tables and Pivot Charts useful. If you are
content with the features now available when you develop in Access 2000,
that would be a valid option for you, though, as I pointed out in the first
paragraph, you should have no difficulty with MDB files made in Access 2003
running in Access 2002 and vice-versa, and MDEs made with 2002 may well run
under 2003.

 Larry Linson
 Microsoft Access MVP