Mail files and Address Book are kept in entirely different locations.
For mail files you will want sent.dbx, deleted.dbx, drafts.dbx and/or inbox.dbx.
I'm not on my WinXP machine right now, but they are located something like:
C/documents and settings/(user)/identities/etc.......as the above person said, do a search for dbx files. Then copy or drag these things to a safe location after which you can "import" them back into Outlook Express when you have things fixed. I back up my mail files by copying these things periodically or exporting them onto my D drive.
Address Book is a little easier to find and manipulate, its somewhere in C/Program Files/Outlook Express.
Email me me if you have any questions.