I would like to setup a public calander which alerts all users that are part of this when apointments come up. i am using exchange 2003 not too sure if this is possible to setup or not.
Outlook doesn't support Alerts/Reminders from Public calendars.
From MS KB 186689 "XCLN: Reminders Do Not Start for Items in Public Folders":
You can get the functionality by using an add-on such as the "Extended reminder function for Microsoft® Outlook®, Public ShareFolder und Microsoft® Exchange Server":