Windows NT 4.0 vs Windows 2000/Windows Server 2003

Differences between Windows NT 4.0 and Windows 2000 / Windows Server 2003:

Windows NT4.0	Windows 2000/Windows Server 2003
The main server is called Primary Domain Controller (PDC).	The main server is called Domain Controller (DC)
Backup Server is called Backup Domain Controller (BDC).	Backup Server is called Additional Domain Controller (ADC).
WINS (Windows Internet Naming Service) is used to identify client computers.	DNS (Domain Naming System) is used to identify client computers.
Supports a maximum of 40,000 user accounts.	Supports more than 160,000 user accounts.
Does not have Active Directory (AD).	Has Active Directory (AD).
Has low security.	Has high security.
Has a flat structure.	Has a heirarchical structure.