Outlook 2003

While Configuring MS Outlook 2003 i have checked “Leave a mesagae in Server”. Now the issues what is happening to me is that after formating my system when i have reconfigured my outlook and made the defalut PST (which was earlier), i have found all the mails which are already there is again downloading from the server.

Can anybody help on this, so that only the new mails get downloaded.