You might try this freeware tool.
Viewer for standalone files containing Microsoft Outlook Express 4,5 and 6 message database (*.idx/*.mbx/*.dbx) and standalone EML files. This application is based on MiTeC Outlook Express Reader. It displays list of contained messages and their header. Message can be viewed in detailed view including attachments (save ability) and HTML preview and printing. Messages can be saved to *.eml files.http://www.mitec.cz/oeview.html
After your open it, go to the top where it says File, and choose Open. Browse to the folder where the .dbx files are. Select the .dbx file you want to see, ie Inbox.dbx, highlight it, select Open.
All the emails in the Inbox are now listed. Highlight the email you want, and then go to the top to Message Database, and select Message View. And there it is!
Or if you just want to save the complete folder first and then look at all of them, just highlight all the messages in the .dbx folder, go up to Message Database and choose "Save Selected" and save them to a folder of your choice, say in My Documents. If you need to put any of them back into your OE Inbox, Sent, a special folder...wherever...you can drag and drop them into OE again.