This is the software publisher's description.

PstPassword is a small utility that recover lost password of Outlook .PST (Personal Folders) file. This utility can recover the PST passwords of Outlook 97, Outlook 2000, Outlook XP, Outlook 2003, and Outlook 2007. You don't have to install MS-Outlook in order to use this utility. You only need the original PST file that you locked with a password.

The password encryption in the PST file is very weak, and for each password-protected PST file, there are many passwords that can open it. PstPassword provides 3 different passwords for each password-protected PST file. It's possible that one of them will be the original password that you typed, and it's also possible that none of these passwords will be identical to the original one. However, all 3 passwords provided by PstPassword will open the PST file without problems.