Windows 2000 Professional was designed as the desktop operating system for businesses and power users. It is the basic unit of Windows 2000, and the most common. It offers greater security and stability than many of the previous Windows desktop operating systems. It supports up to two processors, and can address up to 4 GB of RAM. The system requirements were a Pentium Processor @133 MHz or greater, at least 32 MB of RAM, 650 MB of hard drive space, and a CD-ROM drive (recommended: Pentium II, 128 MB of RAM, 1 GB of hard drive space, and CD-ROM drive).
Windows 2000 Server products share the same user interface with Windows 2000 Professional, but contain additional components for running infrastructure and application software. A significant component of the server products is Active Directory, which is an enterprise-wide directory service based on LDAP. Additionally, Microsoft integrated Kerberos network authentication, replacing the often-criticised NTLM authentication system used in previous versions. This also provided a purely transitive-trust relationship between Windows 2000 domains in a forest (a collection of one or more Windows 2000 domains that share a common schema, configuration, and global catalogue, being linked with two-way transitive trusts). Furthermore, Windows 2000 introduced a DNS server which allows dynamic registration of IP addresses.
Windows 2000 Advanced Server is a variant of Windows 2000 Server operating system designed for medium-to-large businesses. It offers clustering infrastructure for high availability and scalability of applications and services, including main memory support of up to 8 gigabytes (GB) on Physical Address Extension (PAE) systems and the ability to do 8-way SMP. It has support for TCP/IP load balancing and enhanced two-node server clusters based on the Microsoft Cluster Server (MSCS) in the Windows NT Server 4.0 Enterprise Edition. A limited edition 64-bit version of Windows 2000 Advanced Server was made available via the OEM Channel. It also supports failover and load balancing.
Windows 2000 Datacenter Server is a variant of the Windows 2000 Server that is designed for large businesses that move large quantities of confidential or sensitive data frequently via a central server. As with Advanced Server, it supports clustering, failover and load balancing. Its minimum system requirements are normal, but it was designed to be capable of handing more advanced hardware—for instance it was capable of supporting computers with up to 32 CPUs and 64 GBs RAM. A limited edition 64-bit version of Windows 2000 Datacenter Server was made available via the OEM Channel.
www.microsoft.com/windows2000