Never export to and import from a PST.  It's unnecessary and you lose data.

To copy the contacts from OL 2003 to OL 2002, click File>New>Outlook Data
File.  Select "Outlook 97-2002 Personal Folders File (.pst)" and click OK.
Browse to the Windows folder whete you want it stored (or accept the
default), give it a file name (or accept the default, but I'd give it a name
like "Transfer" or "OL2002"), and click OK.  Give it a display name (or
accept the dfefault, but I'd name it so as to match the file name so that
when you add it to the other Outlook it doesn't show up as "Personal
Folders") and click OK.  The PST will be added to your Outlook Folder List
and will contain one subfolder, Deleted Items.  Now, right-click and drag
your main Contacts folder to the root of the new PST (named "Transfer", or
"OL2002", or whatever display name you chose), release the mouse button, and
choose Copy.  When the copy completes, right-click the new PST's root and
choose Close.  Close Outlook.

Transfer the file to the other PC, placing it in a folder that does NOT
contain a PST with the same name, remove any read-only attribute (in Windows
Explorer, right-click, choose Properties, uncheck Read-only), then start
Outlook.  In Outlook, click File>Open>Outlook Data File.  Browse to the
folder where you put the transferred PST, select it, and click OK.  It will
now be added to your Folder List in the second Outlook.  Expand it and click
the Contacts folder in it to display that folder's contents.  Press CTRL-A
to select all of the items in it, then right-click and drag the selection to
your main Contacts folder.  Release the mouse button and choose Copy.  When
the copy completes, right-clickt eh root of the transferred PST and choose
Close to remove it from the folder list.