The address book was dropped years ago, all OL addresses are in the Contacts
Folder, which itself is contained within the *.pst file along with all your
mail.
You may see a window headed OL Address Book in some circumstance when
managing your contacts, this is an internal name, it is not a seperate file.
Actually, both Outlook 2000 and 2003 can use the Personal Address Book,
but support for it is diminishing. One thing that has kept me from moving
entirely to using Contacts is that importing from the PAB always seesm to
make hash of the entries. I don't have time to tinker with them, so I
always go back to using the PAB.