Microsoft Outlook XP and 2003 added a feature called “Person Names Smart Tags” which occasionally can cause delays when opening messages. The tags add an icon by a sender’s name in the preview pane; it’s primarily there for integration with Windows Messenger or MSN Messenger to tell you if the sender is online. You can also access some other info about the sender in Outlook from the menu that drops down.
I don’t know anyone using any of those features, and disabling the tags might speed things up a bit. In Outlook, click on Tools / Options / Other, and uncheck the box for Enable the Person Names Smart Tags.