For about a year or more, my Outlook 2003 PST has been huge (>1 GB), with three sets of Personal Folders, all of which appear to mirror each other. Last month, I set up a new C: drive, with Win 7 Pro x64 (old OS had been XP Pro x32), installed Outlook 2003 there, with no duplicates, but of course they returned when I installed the original PST again. Following an earlier thread, I checked in Control Panel, and found two listings for Personal Folders, the current one in C: and a duplicate in my E:\Data drive. But I doubt this is the cause, as the problem existed under XP, too, and I am pretty certain the stuff on E: is a copy I stored for safekeeping after I installed Win 7. Can I safely delete the duplicates from within Outlook? What can I do to shrink my PST?