A quite clear description of what should happen is in http://www.kellogg.northwestern.edu/kis/docs/outlook/archivebackup-2003.htm: older messages (assuming they weren't imported but received) should be moved from personal foldes.pst to archive.pst. Are you saying nothing is moved?
I have run the autoarchive feature in Outlook to remove old messages but no matter what I do the messages remain in the sub-folders I have created under "Personal Folders." I have instructed the program to use all the same autoarchive properties for all folders under Personal Folders but this still doesn't remove them; I don't want to permanently delete old messages, just archive them. What am I missing?