Only guessing, PST, something to do with Outlook/Outlook Express.
There are some keys: HKLM\SOFTWARE\Classes\CLSID\{00020422-0000-0000-C000-000000000046} HKLM\SOFTWARE\Classes\CLSID\{00020423-0000-0000-C000-000000000046} HKLM\SOFTWARE\Classes\CLSID\{00020425-0000-0000-C000-000000000046}
with Data types of PSTypeInfo, PSTypeLib, PSTypeComp which again kind of seems to relate back to O/OE.
