NT SAM database is a flat database. Where as in windows 2000
active directory database is a hierarchical database.

In windows NT only PDC is having writable copy of SAM
database but the BDC is only read only database. In case of
Windows 2000 both DC and ADC is having write copy of the
database

Windows NT will not support FAT32 file system. Windows 2000
supports FAT32

Default authentication protocol in NT is NTLM (NT LAN
manager). In windows 2000 default authentication protocol is
Kerberos V5.

Windows 2000 depends and Integrated with DNS. NT user
Netbios names
Active Directory can be backed up easily with System state data

Application Server mode is introduced in windows 2003

Possible to configure stub zones in windows 2003 DNS

Volume shadow copy services is introduced
Windows 2003 gives an option to replicate DNS data b/w all
DNS servers in forest or All DNS servers in the domain.

PDC contains a write copy of SAM database where as BDC
contains read only copy of SAM database. It is not possible
to reset a password or create objects with out PDC in
Windows NT.
There is no difference between in DC and ADC both contains
write copy of AD. Both can also handles FSMO roles (If
transfers from DC to ADC). It is just for identification.
Functionality wise there is no difference


windows 2008 is fully script based software with more group
policies and permissions