JSI Tip 4045. How do I back up and restore messages, Address Book, mail accounts, and news accounts in Outlook Express 5 and later?

Microsoft Knowledge Base Article 270670 contains the following summary:

This article describes how to back up and restore your messages, Address Book, mail accounts, and news accounts in Outlook Express 5 and later. If multiple Identities are in use for Outlook Express, these steps should be repeated for each Identity and the backup data segregated accordingly. This will facilitate restoration of each Identity.