Outlook 2003 pst files mail items slow to load

[Alan Culshaw]

I have a customer using outlook 2003 and pop3 as his mail
collection. The data is stored in PST files on each local
machine. Opening any mail item takes about 45 secs with
outlook not responding for some of the time. The machines
that still have outlook 2000 do not have this problem. I
have removed the "remove extra lines" option. Once you
open any mail item you can reopen it quickly untill the
next time outlook restarts.

Any suggestions