You can only do so in Outlook 2003 by creating a new PST file in the old
format and copying your data into it.
File > New > Outlook Data File...

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Russ Valentine
[MVP-Outlook]
> I'm wanting to migrate my system to new upgraded hardware (asked a
> question about this earlier) but I now realise I've made a software
[quoted text clipped - 4 lines]
>
> How can I convert an outlook 2003 PST to an outlook 2002 PST ????