Outlook (Entourage for Mac which is what i have) is a great program to use as your email client, address book, calendar, and ToDo manager. I sync my file with a palm pilot (PDA) and my digital schedule book is automatically updated and with me everywhere.

There is also quite a bit of info stored in emails that are organized in folders according to client, subject etc. In short, there is a LOT of valuable information stored in my Entourage (Outlook for you PC users) user data file.

Working with a client yesterday, I found that her Outlook user data file wasn’t in My Documents, which is where we are consolidating her user files for easy backup. Going through the help files, I came across:
http://www.microsoft.com/downloads/details.aspx?FamilyID=8b081f3a-b7d0-4b16-b8af-5a6322f4fd01&DisplayLang=en

to back up all the folders, calendar items etc. Then, for a great explanation of how to use it and restore data:
http://office.microsoft.com/en-us/assistance/HA010875321033.aspx