In Outlook 2003. Sorry, it's not part of Express. You could open up the .dbx files in:

C:\Documents And Settings\<username>\Local Settings\Application Data\Identities\<some code>\Microsoft\Outlook Express

Or just do a search for .dbx files and be sure to include hidden files. You can open the files in a tool like MailNavigator (no experience, it came up first on Google) to recover any emails that haven't been purged yet.

If the stores have already been purged, you're pretty much up a creek. Learn to back up! Mozy is a good always-on set-it-and-forget-it online backup.