I sometimes have to deal with customer computers whose Outlook PST or OST files have become corrupted. Very often the fix is to run SCANPST.EXE on the offending PST/OST file.
However, every time I go to do this I forget where the two executable files are. Here is where they are on a Vista machine running Office 2007:
C:\Program Files\Microsoft Office\Office12
I hope this helps.