I'm not sure copying the raw files will work... I would test it first. It used to work with outlook and outlook express but Outlook 2003 has some "security features" that can prevent that from going smoothly.
For a sure thing, use Export under the file menu. Then in your fresh Outlook, import it back in.
UNLESS, is this a work account, or are you connecting to an Exchange server, instead of POP? If so, then you don't need to do anything, your email is on the server. Connect with the fresh Outlook, and the first thing it will do is download all your mail, contacts and calendar again. Same with IMAP, but only for the messages, you'll still need to export-import your contacts and calendar.
If you really want a perm backup, a cool way to do it is open a GMail account, turn on IMAP for it, addit as an account in your outlook, and just drag and drop your email folders onto it. That will copy all your current messages and attachments, it is pretty slick. I did that for my last two jobs and have that whole store (and the search is much, much faster than Outlook 2003.