Windows 2000

Windows 2000, also known as Windows NT 5.0, was the last version of the Windows NT line of operating systems which was released for business users only and succeeded Windows NT 4.0. It is still branded with "Based on NT Technology", possibly to prevent confusion with the 9x line (which was also named after the year of release at that time). This was done between Beta 2 and 3 stages, somewhere between builds 1911.1 and 1946.1. Extended support ended in 2010. It is the last version of Windows NT to include NT in its product name.

Editions
Windows 2000 was released in Workstation (Professional) and Server (Advanced Server, Datacenter Server, Server) editions.

 Information about each edition borrowed from Wikipedia, the free encyclopedia.

Professional
It is the client version of Windows 2000. 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 are a Pentium processor (or equivalent) of 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, 2 GB of hard drive space, and CD-ROM drive).

Server
It shares the same user interface with Windows 2000 Professional but contains additional components for the computer to perform server roles and run infrastructure and application software. A significant new component introduced in the server versions 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 catalog, being linked with two-way transitive trusts). Furthermore, Windows 2000 introduced a Domain Name Server which allows dynamic registration of IP addresses. Windows Server 2000 supports up to 4 processors, requires 128 MB of RAM and 1 GB hard disk space, however requirements may be higher depending on installed components.

Advanced Server
It is a variant of Windows Server 2000 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 supports TCP/IP load balancing and enhanced two-node server clusters based on the Microsoft Cluster Server (MSCS) in Windows NT Server 4.0 Enterprise Edition. Limited number of copies of an IA-64 version, called Windows Advanced Server 2000, Limited Edition were made available via OEMs. System requirements are similar to those of Windows Server 2000 however, they may need to be higher to scale to larger infrastructure.

Datacenter Server
It is a variant of Windows Server 2000 designed for large businesses that move large quantities of confidential or sensitive data frequently via a central server. Like Advanced Server, it supports clustering, failover and load balancing. Its minimum system requirements are normal, but it was designed to be capable of handling advanced, fault-tolerant and scalable hardware—for instance computers with up to 32 CPUs and 64 GBs RAM, with rigorous system testing and qualification, hardware partitioning, coordinated maintenance and change control. A limited number of copies of an IA-64 version of Windows Server 2000, called Windows Datacenter Server 2000 Limited Edition were made available via OEMs. System requirements are similar to those of Windows Advanced Server 2000 however, they may need to be higher to scale to larger infrastructure.

Service Packs
In all, there were four service packs released for Windows 2000. All are considered as abandonware as of 2013.

Service Pack 1
Service Pack 1 was released on 15 August 2000.

Service Pack 2
Service Pack 2 was released on 16 May 2001.

Service Pack 3
Service Pack 3 was released on 29 August 2002.

Service Pack 4
Service Pack 4 was released on 26 June 2003.

Update Rollup 1
Update Rollup 1 for Service Pack 4 is a collection of hotfixes, mainly for the security-related issues. It is said to contain all the security-related hotfixes and some non-security updates released between SP4 and UR1 for SP4. This rollup has been released instead of Service Pack 5. 

Microsoft also planned to release Service Pack 5, but it was canceled and the Update Rollup 1 for Service Pack 4 was released instead. 

Pre-Beta

 * Windows NT 5.0 Build 1515.1
 * Windows NT 5.0 Build 1516.1
 * Windows NT 5.0 Build 1575.1
 * Windows NT 5.0 Build 1580.1
 * Windows NT 5.0 Build 1585.1
 * Windows NT 5.0 Build 1592.1
 * Windows NT 5.0 Build 1597.1
 * Windows NT 5.0 Build 1627.1
 * Windows NT 5.0 Build 1631.1
 * Windows NT 5.0 Build 1645.1
 * Windows NT 5.0 Build 1661.1

Beta 1

 * Windows NT 5.0 Build 1671.1 - Official Beta 1
 * Windows NT 5.0 Build 1691.1
 * Windows NT 5.0 Build 1701.1
 * Windows NT 5.0 Build 1717.1
 * Windows NT 5.0 Build 1723.1
 * Windows NT 5.0 Build 1729.1
 * Windows NT 5.0 Build 1738.1
 * Windows NT 5.0 Build 1743.1
 * Windows NT 5.0 Build 1745.1

Interim Developer Release

 * Windows NT 5.0 Build 1773.1
 * Windows NT 5.0 Build 1796.1

Beta 2

 * Windows NT 5.0 Build 1814.1
 * Windows NT 5.0 Build 1816.1
 * Windows NT 5.0 Build 1828.1
 * Windows NT 5.0 Build 1835.1
 * Windows NT 5.0 Build 1848.1
 * Windows NT 5.0 Build 1855.1
 * Windows NT 5.0 Build 1859.1
 * Windows NT 5.0 Build 1868.1
 * Windows NT 5.0 Build 1877.1 - Official Beta 2
 * Windows NT 5.0 Build 1902.1
 * Windows NT 5.0 Build 1906.1

Beta 3

 * Windows NT 5.0 Build 1911.1
 * Windows NT 5.0 Build 1916.1
 * Windows NT 5.0 Build 1930.1
 * Windows NT 5.0 Build 1946.1 - Official Beta 3 Release Candidate 0
 * Windows NT 5.0 Build 1952.1
 * Windows NT 5.0 Build 1964.1
 * Windows NT 5.0 Build 1965.1
 * Windows NT 5.0 Build 1969.1
 * Windows NT 5.0 Build 1976.1
 * Windows NT 5.0 Build 1983.1
 * Windows NT 5.0 Build 1989.1
 * Windows NT 5.0 Build 1993.1
 * Windows NT 5.0 Build 1994.1
 * Windows NT 5.0 Build 1996.1
 * Windows NT 5.0 Build 1999.1
 * Windows NT 5.0 Build 2000.1
 * Windows NT 5.0 Build 2000.3 - Official Beta 3 Release Candidate 1
 * Windows NT 5.0 Build 2016.1
 * Windows NT 5.0 Build 2020.1
 * Windows NT 5.0 Build 2031.1 - Official Beta 3
 * Windows NT 5.0 Build 2035.1
 * Windows NT 5.0 Build 2040.1
 * Windows NT 5.0 Build 2042.1
 * Windows NT 5.0 Build 2068.0

Release Candidate 1

 * Windows 2000 Build 2072.1
 * Windows 2000 Build 2091.1
 * Windows 2000 Build 2092.1
 * Windows 2000 Build 2124.1

Release Candidate 2

 * Windows 2000 Build 2128.1
 * Windows 2000 Build 2151.1
 * Windows 2000 Build 2167.1
 * Windows 2000 Build 2183.1

RTM

 * Windows 2000 Build 2195.1

SP1 RTM

 * Windows 2000 Build 2195.1620

SP2 RTM

 * Windows 2000 Build 2195.2951

SP3 RTM

 * Windows 2000 Build 2195.5438

SP4 RTM

 * Windows 2000 Build 2195.6717

Small Business Server Beta

 * Windows 2000 Build 1059.0