You can be benefited by the side affect of a microsoft utility pst19upg.exe. This utility is used to upgrade the old version of .pst file and when you use this utility it removes the old password of .pst file.
For details visit: *www.slipstick.com/problems/lostpw.asp
You can also try some 3rd party pst password recovery software which could recover loss or forgotten pst password more efficiently.
Detailed information: *www.pst-password-recovery.com/password-repair.php
i have forgotten my outlook personal folder password... pleas help!!!