Dick,
NTUSER.DAT gets backed up without any problems for those users that are not
currently logged in during backup time.
For the users logged on the contents of NTUSER.DAT are backed up together
with the registry. After a restore you'd find this information in
C:\ADSM.SYS
\---Registry
    \---PC5622
        +---Machine
        |       Sam
        |       Security
        |       Software
        |       System
        |
        \---Users
            |   Default
            |
            +---ppomb
            |       S-1-5-21-2130729834-1554841893-515445417-7181
(=NTUSER.DAT)
            |
            \---SYSTEM

Regards,
Michael