How do I restore the deleted items folder?

In my Outlook 2003, the deleted items folder will not display - it comes up
blank with "unable to display folder" on the page. It is not possible to
empty it, that messge says "can not delete items, unknown error, please
re-start Outlook" but this has no effect. At the same time, I am getting
duplicates of emails previously received every time I log on, (around 8 times
each message) which means that the deleted items folder is quite full I
suppose? Any ideas please?