We have a public calendar that users can invite to meetings, but it has an annoying problem. When a user opens an appointment from the public calendar, Microsoft Office Outlook 2003 automatically copies the item to the user's personal Calendar folder. How can we prevent that from happening?

The reason items are copied to users' personal Calendar folders is that the calendar folder in the Public Folders hierarchy is mail-enabled so that users can invite it to meetings. There are two solutions to this problem. One solution is to upgrade to Microsoft Office Outlook 2007, which doesn't exhibit this behavior because Microsoft changed how meeting requests are processed in Outlook 2007. The other solution is to stop using a public folder—which isn't designed to function as a public calendar for scheduling purposes—and instead create a mailbox to host the calendar, as you would for a conference room or other resource calendar. Microsoft Exchange Server 2007 includes explicit support for room and equipment mailboxes, making resource scheduling much easier, so you might consider migrating to Exchange 2007.