When you use Outlook 2003 and open other people's calendars as a secondary mailbox in your profile, the calendars will all have the highly descriptive display name of "Calendar". When you open the calendars as a shared calendar the owner's name is used instead.

So... even if you have the calendars open as a secondary mailbox in your profile, add then to the Other Calendars section using the Open a Shared Calendar link in the navigation pane. When you need to view them, click on the calendar in the Other Calendars section.