The file you need to back up is your Personal Folders file (*.pst) It's
where all the mail, calendar, contacts etc are stored.
Take a look at these pages for info on Outlook data backup:
http://www.slipstick.com/config/backup.htm
http://www.howto-outlook.com/Howto/backupandrestore.htm

Signature
Russ Valentine
[MVP-Outlook]
> i recently suffered a fatal motherboard and hard drive failure which
> involved completely reformatting my hard drives. i regularly back up my
[quoted text clipped - 8 lines]
> whereby i can file all this information elsewhere to allow me to back - up
> without have to fill in those countless windows for each contact. HELP