Right-click on the header row and select Field Chooser. Add whatever fields
you want to the view. Then drag them around to position them wherever you
want.
Make sure you're using the Messages view. If you are already, reset the view.
Exactly how is version-specific and you decided to keep that informaiton
secret. In Outlook 2003, you'd click View>Arrange By>Current View>Customize
Current View>Reset Current View.