Ok, here's what to do:
Open up your copy of Outlook (if you don't have one, we could have a problem here)
Create a new folder, of type: Contacts. Call it ClientContacts or something.
Click into it.
Click File, Import and Export, Import from another program or file, Personal folder File (.pst).
Locate the PST file.
Select the Contacts list in the menu and check the "Import items into current folder" button.
Then click Finish..
Then Export the ClientContacts folder as an excel spreadsheet or CSV file.
Et voila!