I can handle this one. This is something I do regularly, and ran into that problem.
When Outlook is closed and you've dropped in the PST file (must rename the existing) You will notice the contact won't pull up when you try to add one to an email.

Tools>Options>email accounts> view/change existing directory. Delete what ever addressbook you have working currently.
Restart Outlook
Add Address book>Additional Address book>Outlook address book.

Thats all it should take.

If possible do a PST export from your old email then import "from another program or file" and select PST.