To repair large PST files bigger than 4 GB, the following must be installed on the computer:
If they are, the Outlook Repair Toolbox program is not limited by the amount of data it can handle in 32-bit systems and will be able to completely restore and save the data in a new PST file.
If Microsoft Outlook 32-bit is installed on the computer, then the operation of the Outlook Repair Toolbox program is limited by the RAM that is needed to work with large PST files. If the installation disk or software distribution package is available, Microsoft Outlook 64-bit can be installed instead of the 32-bit version of Microsoft Outlook. For more detailed information about installing the 64-bit version of Microsoft Outlook, please consult the specific article.