I'm really not following what you are asking, but it seems like you want to
know why there is a file size limit of 2GB on PST files for Outlook 97/2002.
The biggest reason why is that legacy file systems like FAT or sometimes
referred as FAT16 will only allow a file size of 2GB.
Outlook 2003 will only be supported on Windows 2000 (SP3) and newer systems.
The new PST file structure will default to a file size limit of 20GB but can
be adjusted upwards.