To merge the PST files in MS-Outlook then trying to use of KDETools PST Merge. It joins Various PST files in MS-Outlook. It Combines PST files such as Emails, Contacts, Calendars, Tasks and all. It supports in all Version of Windows and Outlook. During Joining PST files this tool easily removes the duplicates PST files. It joins only selected PST files or folders. Capable in ANSI and also UNICODE formats. It has not required of MS-Outlook.
More Info: http://www.merge-pst.com/