Delete Won't Work Correctly

When I'm in Outlook Express, hitting the Delete key or using the mouse to delete emails only works for emails already in the recycle bin. Delete won't work for email in the Inbox or Sent Items folders. I've run Registry Patrol and Avast, even installed Version 7 of Outlook Express thinking that might solve the problem, but nothing I've tried has worked.

Anyone have an idea of what the problem is and/or how to correct it? If the fix is reinstalling Outlook Express, where do I find that specific download?