A damaged Personal Storage Table (.pst) file is the #1 cause of Microsoft Outlook problems. A .pst file stores your e-mails, calendar entries, contacts, and other Outlook data. Think of a .pst file as a local database for Outlook.
If Outlook ever fails to start or stops functioning normally, follow these steps to repair your Outlook .pst file:
1. Close Microsoft Outlook
2. Navigate to \Program Files\Microsoft Office\OFFICE12
3. Double-click on scanpst.exe
4. Click on “Browse” to select your .pst file
5. Click on “Start”
6. Click on “Repair” (Note that you only see this option if Outlook finds errors)