Outlook Client Downloads mail twice

I installed an Outlook 2003 client for an existing user on a new laptop(internet version- the server is at a remote location)and it attempted to download all the mail from the Exchange 5.5 Server a second time. I had already moved the pst files from the old laptop to the new, so the download resulted in duplicate mail (I stopped the download just after it started since the user had 26K messages on the server). How can I stop the Outlook from downloading all the mail a second time?