The Personal Address Book (PAB) is not supported in Microsoft Office Outlook 2007. By default, users are prompted when Outlook first starts to migrate the PAB contents into a Contacts folder they choose. This setting allows you to change migration behavior so that users are not prompted. You can choose to:
1) migrate users' PAB contents automatically to the Contacts folder (the default Outlook Address Book) when Outlook first starts (silent migration) and remove the PAB from users' profiles
2) just remove the PAB from users' profiles. Removing the PAB from profiles does not delete the PAB files; they can be imported later using Import and Export on the File menu.