What happened to my Outlook Express email?

I came home and turned on the computer.  After awhile I returned to see a message that Norton's was "reconfiguring" Outlook Express.  When I tried to access my inbox I discovered that about 6 months worth of my inbox messages were gone and that ALL of my sent messages were deleted.  I still need/want those files.  What did Norton's do with it?  How do I retrieve those files?  I'm running XP, Norton's Internet Security, IE9.  Can anyone help?