Open Outlook Express (OE), on then left pane, right click "Local Folders", select "New Folder...", specify a name for you new folder as "Temp"
If you are still able to accress "Inbox", move all mails in "Inbox" to the new "Temp" Folder.
Go to menu "Tools" -> "Options" -> "Maintenance" tab -> "Store Folder" button. It will show the location of your Inbox file, please remember this location.
Close Outlook Express (OE), go to the location mentioned above, delete the file "Inbox.dbx"
Restore Outlook Express (OE), the "Inbox" folder should be auto recreated. Move back your mails to the new "Inbox", remove the "Temp" folder.