Wish I had a recommendation on software...
However, with a certain level of updates, maybe XP SP2 or so, you should note that Outlook Express makes backups in the recycle bin of it's DBX files when it compacts them. Each .DBX file will be found as a .BAK in the bin.
Last time I had a call for corrupted DBX files, (they must have been corrupted during the compacting process), all I had to do was restore the originals.
If nothing else maybe there is a copy in there from an earlier compacting process.
Worth a look...