How to Backup Your Outlook Data
The Personal Folder file (.pst) is where Outlook stores data.
Each Personal Folder file contains all of your Outlook folders, including Inbox, Calendar, and Contacts. There may be a single .pst file (usually called "Internet Folders" or "Personal Folders" in your Outlook Folder List). There may also be an additional .pst file used to archive messages (usually named "Archive Folders").
Back up these PST files to back up all Outlook information. Backing them up is easy, just copy them to a safe place with Right-Click --> Copy followed by Right-Click --> Paste.
The hard part is finding the PST files...
You also may want to check out the Microsoft Outlook Personal Folders Backup tool, more information and download link are available at: http://office.microsoft.com/en-us/outlook-help/using-the-microsoft-outlook-personal-folders-backup-tool-HA001087532.aspx