Outlook is a complete pain in the wotsit with where it stores and how it manages files.
I tend to use this little add in from Micro$oft
Download details: Outlook 2003/2002 Add-in: Personal Folders Backup that makes managing them easier - you may have it already but it is easier than File-Import/Export.
What I would suggest to be on the safe side is for you to open your outlook account and back it up and then SWMBO does the same with hers.
Good luck!