2-part question -- 1) Where are outlook address book entries kept
under outlook 2000 and outlook XP? (I know Outlook XP can link to
"Contacts", but I'm not referring to Contacts -- I'm referring to the
actual address book entries)... 2) If I have a full backup of a system
(using XP's built in "ntbackup.exe") that contained an installation of
Outlook 2000 with outlook address book entries, is there any way to
restore address book entries? (just the address book entries, not a
full restore)

If you are using Outlook 2000 or older, the address book is kept in a
file with the extension of .pab for personal address book.  It would
be the profilename.pab.  I'm not sure if Outlook XP still is able to
use this.  If so, the next version of Outlook may not be able to so
you should consider importing them into your contacts.  To do this,
find the .pab file.  Open Outlook.  Click File, Import and Export,
Import from another program or file and click Next. Select Personal
Address Book and click Next.  Browse to find the .pab file and click
Next and complete the import.

I know you can export to PAB's, but I'm not certain as to where they
are kept, by default, without having to export.

If you do a search for *.pab you'll find all the personal address book
files on your computer.  There is one per profile.