To access the PST file you must either use Outlook code or an alternative
API that allows logging into a PST file without using Outlook code. CDO 1.21
can do that but is not supported for .NET code, nor is Extended MAPI (C++ or
Delphi only anyway). You could use a .NET safe 3rd party library such as
Redemption (www.dimastr.com/redemption) but I'd probably just automate
Outlook using a custom action in the uninstaller.

Doing so may bring up prompts to log into Outlook if the user has set to
prompt on starting Outlook. A custom action script might also be blocked
from running by a script stopper, such as the ones in various anti-virus
products.