The best thing to do is simply copy your Outlook data file and set your new
installation to use that same file as its default. The file you need to 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