Microsoft provides the Inbox Repair Tool for correcting most problems with damaged PST.
When you run Scanpst.exe, it performs a number of tests. If it finds errors, it asks whether you want to make a backup copy of the original file (always say Yes), then tries to correct the errors. For seriously corrupted PST files, try running Scandisk.exe first, then Scanpst.exe, repeating 3-4 times until neither program returns an error. We’ve known this technique to restore data that the user thought was lost forever.