I haven't done this in Outlook Express, but it's worked for me in MS Outlook before. Copy the original dbx files should be found under root:\docs and settings\<user name>\local settings\application data\identities\<random identity>\microsoft\outlook express ..
When you copy them rename them, for example NewInbox.dbx then rename the old dbx and save to a location on your computer where you will remember where they're at just in case. Open Outlook and have File>Import to get it to try and locate the dbx files with the new name.
Let me know if it works. As I've said, I've used this in Outlook where the user gets a large file "stuck" in their outbox because the program tries sending it before it realizes it's too big, and then won't let the user delete it.
May try saving the DBX files to a safe location and then removing outlook express and re-install it first before trying to import them back in. But note that this will only be the e-mail messages, not address book and such.
