If you can't open your Personal Folders file (.pst) (Personal Folders file (.pst): Data file that stores your messages and other items on your computer. You can assign a .pst file to be the default delivery location for e-mail messages. You can use a .pst to organize and back up items for safekeeping.) or your Offline Folder file (.ost) (Offline Folder file: The file on your hard disk that contains offline folders. The offline folder file has an .ost extension. You can create it automatically when you set up Outlook or when you first make a folder available offline.), or you suspect that your .pst or .ost data file is corrupt, you can use the Inbox Repair tool (Scanpst.exe) to diagnose and repair errors in the file. The Inbox Repair tool scans only the .pst or .ost file, making sure that the file structure is intact. It doesn't scan your mailbox on the Microsoft Exchange Server. The Inbox Repair tool will reset your file structure and rebuild headers.
The Inbox Repair tool works on both the Microsoft Outlook 97-2002 Personal Folders File (.pst) and the Outlook Personal Folders File (.pst) data files.
Scanpst.exe is installed when you install Microsoft Outlook and is located at:
drive:\Program Files\Common Files\System\MSMAPI\LocaleID folder - where LocaleID is the locale identifier (LCID) for the installation of Microsoft Office. The LCID for English - United States is 1033.
Note If you get error messages when you synchronize your .ost file with the Exchange server, you should use the OST Integrity Check tool.