Outlook 2003 supports 2 different types of PST files.
1) Office Outlook Personal Folders File - 20GB max file size (soft limit and
can be adjusted via registry key). Unknown item limit. Supports Unicode
character set. This PST file type is not backward compatible.
Note: FAT32 formatted drives can only support a file with a max size of 4GB.
2) Outlook 97/2002 Personal Folder file - 2GB max file size (hard limit).
65,000 item/folder count limit. No support for Unicode. This PST file type
is compatible with Outlook 97/2002.
#1 is the default type used in most cases. (IMAP accounts being the
exception where it uses #2)
If upgrading from a previous version of Outlook or using a PST file from a
previous version, Outlook 2003 does not automatically upgrade the PST file
type. Requires import/copying the items from #2 to #1 type PST.
