**Windows 2000** (also known as **Win2K**, **W2K**, **Win2000** or **Windows 2K**) is an operating system for computers that have either single or multiple processors. It was made for 32-bit Intel x86 computers. It is part of the Microsoft Windows NT line of operating systems, and was released on February 17, 2000. Windows 2000 comes in four versions: Professional, Server, Advanced Server, and Datacenter Server. Additionally, Microsoft offers Windows 2000 Advanced Server - Limited Edition and Datacenter Server - Limited Edition, which were released in 2001 and run on 64-bit Intel Itanium processors. Windows 2000 was designed for businesses, but it was also popular with home users.

Windows 2000 uses two 'modes' - a 'User Mode' and a 'Kernel Mode'. The Kernel Mode is specially for hardware drivers (drivers tell the computer how to 'speak' to something) and allows drivers to 'speak' to things in the computer. The User Mode is for computer programs to run in without fear of causing harm to the computer.

All versions of Windows 2000 have things in common, including many system utilities such as the Microsoft Management Console (MMC) and standard system management applications such as a disk defragmentation utility. There is lots of support for different languages and for people with disabilities. Windows 2000 supports the Windows NT file system NTFS 5, the Encrypted File System (EFS), as well as basic and dynamic disk storage. Dynamic disk storage allows different types of volumes to be used (a volume is an area of storage on a hard disk that has been formatted with its own file system structure). The Windows 2000 Server version has many more features, including the ability to provide Active Directory services (a way of organising resources such as printers, users and group), a distributed file system (a file system that supports sharing of files) and fault-redundant storage volumes.

Windows 2000 can be installed and deployed to an enterprise through either an attended or unattended installation. Unattended installations rely on the use of answer files to fill in installation information, and can be performed through a bootable CD using Microsoft Systems Management Server (SMS), by the System Preparation Tool (Sysprep).

History
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Windows 2000 was created from the Microsoft Windows NT operating system versions. It was originally called Windows NT 5.0 but Microsoft changed the name to Windows 2000 on October 27, 1998. The first software test version (also known as a beta version) for Windows 2000 was released on September 27, 1997. Several more test versions were released until Beta 3, which was released on April 29, 1999. Microsoft further issued three more test versions from between July to November 1999. They then finally released Windows 2000 to partners on December 12, 1999. The public received the full version of Windows 2000 on February 17, 2000 and the press immediately called it the most stable operating system Microsoft had ever released. Novell (a competitor of Microsoft) did not think that Microsoft's new directory service product (part of Windows 2000) was as good as their own Novell Directory Services (NDS) technology. On September 29, 2000, Microsoft released Windows 2000 Datacenter. Microsoft released Service Pack 1 (SP1) on August 15, 2000, Service Pack 2 (SP2) on May 16, 2001, Service Pack 3 (SP3) on August 29, 2002 and its last Service Pack (SP4) on June 26, 2003. Microsoft has said that they will not release a Service Pack 5, but instead, have offered an "Update Rollup" for Service Pack 4. Microsoft stopped developing their Java Virtual Machine (JVM) for Windows 2000 in Service Pack 3.

Microsoft has replaced Windows 2000 Professional with Windows XP Professional, and Windows 2000 Server products with Windows Server 2003. A project code named "Neptune" started development in 1999. Neptune was based on Windows 2000, and it was supposed to be a home-user replacement for Windows 98. However, the project took a long time to create and only one pre-test (alpha version) release was created. Windows Me was released instead, and the Neptune project later turned into part of a project that became Windows XP. The only elements of the Neptune project which were included in Windows 2000 were the ability to upgrade from Windows 95 or Windows 98, and support for the FAT32 file system.

Several notable security flaws have been found in Windows 2000. Code Red and Code Red II were famous computer worms that used problems with the indexing service from Windows 2000's Internet Information Services (IIS) to cause security problems. In August 2003, two major worms named the Sobig worm and the Blaster worm began to attack millions of Microsoft Windows computers and caused many problems for system administrators and computer operators who used Windows 2000. This was very embarrassing for Microsoft, and caused many corporations and governments to look carefully at Microsoft's security problems.

Windows 2000 is the last version of Windows that does not require any Pentium instructions, and is therefore the last version that will run on an Intel i486.

Other websites
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* Windows 2000 official product page
* Windows 2000 Professional feature list
* Windows 2000 Server Family
* Windows 2000 Server information at Technet
* Official support page
* Windows 2000 Transitions to Extended Support.

| * v
* t
* e
Microsoft Windows |
| --- |
| DOS-based | 
* 1.0x
* 2.x
* Windows 3.x
	+ Windows 3.0
	+ 3.1x
	+ for Pen Computing

 |
| Windows 9x | 
* 95
* 98
* Me

 |
| Windows NT | 

|  |
| --- |
| 
* NT 3.1
* NT 3.5
* NT 3.51
* NT 4.0
* 2000
* XP
	+ Pro x64
	+ Media Center
	+ Fundamentals for Legacy PCs
* Vista
* 7
* 8 and 8.1
	+ RT
* 10
* 11

 |
| Windows Server | 
* Server 2003
	+ Home Server
* Server 2008
	+ EBS 2008
	+ HPC Server 2008
* Server 2008 R2
	+ Home Server 2011
* Server 2012
* Server 2012 R2
* Server 2016
* Server 2019
* Server 2022
* MultiPoint Server
* Server Essentials

 |
| Specialized | 
* Windows Preinstallation Environment
* Windows IoT
* Windows 365

 |

 |
| Windows IoT | 
* Modular Windows
* Embedded Compact
	+ CE 5.0
	+ Embedded CE 6.0
	+ Embedded Compact 7
* Embedded Automotive
* Embedded Industry

 |
| Windows Mobile | 
* Pocket PC 2000
* Pocket PC 2002
* Mobile 2003
* Mobile 5.0
* Mobile 6.0
* Mobile 6.1
* Mobile 6.5

 |
| Windows Phone | 
* Phone 7
* Phone 8
* Phone 8.1
* 10 Mobile

 |
| Cancelled | 
* Cairo
* Nashville
* Neptune
* Triton
* Odyssey
* 10X

 |
| Related | 
* Development
	+ 95
	+ XP
	+ Vista
	+ 10
	+ 11
* Editions
	+ XP
	+ Vista
	+ 7
	+ 8
	+ 10
	+ 11
* New features
	+ XP
	+ Vista
	+ 7
	+ 8
	+ 10
	+ 11
* Removed features
	+ XP
	+ Vista
	+ 7
	+ 8
	+ 10
	+ 11
* Version history
	+ Phone
	+ 10
	+ 10 Mobile
	+ 11
* Criticism
	+ XP
	+ Vista
	+ 10
* Microsoft Plus!
* Vista vs. XP

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| Preceded byWindows 98 |  **Windows Versions**2000-2001 | Succeeded byWindows ME |