I'd look at the last modification dates on those 5 .pst files. Odds are the most recently modified file is the one you're looking for.
Outlook 2000, Windows NT
Opened outlook and all contacts and recent mail is gone. When opened it pulled mail up from a month ago but shows them all as unread messages. It's almost as if it set up a new account. 5 different .pst's exist on my machine.
Any ideas where to start on this one?