Just to add, you could try this method to locate the files:

Open Outlook Express > Tools > Options > Maintenance > Store Folder

Use your mouse to highlight the full path showing (hold your left click down, then run it across everything showing till you get to the end) and while still highlighted, Right click > Copy.

Now open an Explorer Window, ie My Computer, paste your 'Store folder path' in the address bar > Go/Enter, and you now should have all your folders on view. Double click them one at a time to see if it reveals the missing files.

Good luck.