There is a handy tool to strip the password of a pst-file. The funny thing is that this tool wasn’t even written for stripping the password of a pst-file but for upgrading the pst-file to a newer format. Stripping the password was just a (handy) side effect. Don’t use this tool for any illegal activities!!!
Read the pstread.txt file included in the zip before using the utility!
Click here to download.
If this workaround doesn’t work for your pst-file, consider using a tool that has been designed for pst password recovery such as Atomic Pst Password Recovery.