Give a try to Archiving feature, it is often deemed that this feature moves old emails to the other PST file and subsequently the size of the default Outlook PST file gets diminished.
To be frank, your question seems mind-boggling and I have a suspicion that this all is happening because of some sort of corruption or bug which is impeding you to access your Outlook Data File. If there is something like that, you are going to run into a big trouble.
Well, waiting for your reply so I could exactly determine the actual cause of the glitch.
Thanks & Regards