Windows 2003

Windows 2003 is operating system coded and released by Microsoft Corporation.

Support
Technical support for Standard edition ended on 12 July 2010, Extended support Ends on 21 March 2018. Professional technical support ended on 31 September 2011 and Extended Support ends in middle 2020. Home Edition technical Support ended on 15 September 2010, Extended Support Ends on 10 April 2017.

Pre-Alpha
First ever build of Windows 2003 was released in 29 March 2002. Only change is boot screen and theme.

This build has been leaked on 11 August 2002(Pretty fast).

Alpha
Second build of Windows 2003 was released in 17 July 2002 as Windows XP Home Edition 2.0 (joke made by MS coders)

This build has many,many changes:
 * Changed Kernel from 5.1 to 5.2
 * Small change on theme
 * Changed color name od build from dark blue to green
 * Internet Explorer 6.1
 * Windows Media Player 9.1
 * First Attempt to add and finish Longhorn features (Fail)

This build has been leaked on 24 September 2004
 * And many, many more!

Beta 2
Third (Public) and eleven(Private) Build of Windows 2003.

Changes: This Build has been leaked on 30 August 2006
 * Improved security on Internet Explorer
 * Custom version of IE (6.3 with Security fixes and support for newer sites)
 * Added (On private build) Millenium Virus Scanner (By WinSec)
 * Removed completly com files (It caused problems, fixed right after release)
 * Second and sucesfull attempt to add and finish Longhorn features

Pre-RTM/RC1
Fourth(Public) and thirteen(Private) Build, and final from building operating system has small changes: This Build has been leaked on 6 November 2007.
 * Changed Versions of programs (IE 6.3-IE 6.8 SuperSecure Edition)
 * Removed AntiVirus and replaced by Security Fixes
 * Added Firewall Support, CBE (Check-Before-Enter) Function added to IE

Final Build
Final Release of Windows 2003.

Changes:
 * Added Support for third-party themes
 * Finale fixes on security
 * Added DirectX 9.0 and above Support
 * Added GameLib 1.0 (By GameOS)

Not even leaked
 * Added more features to cmd

Home/Professional
Bonus release of Windows 2003 for Home and Office users

Changes for Home Edition: Changes for Professional Edition: Removed Content Not even leaked
 * Removed some features for cmd
 * Added Windows Media Center
 * Limited Firewall
 * Added new account type: Pre-Administrator
 * Improved Firewall, security
 * Added Configure your server
 * Removed support for DirectX 7.0, by adding GameLib 1.1 (By GameOS)
 * Removed Windows Media Player 9.0, by replacing Windows Media Player 10
 * new Update website : msws://update.win2003.microsoft.com)

Trivia

 * Earlier this OS is meant to be Home Editon of Windows 2000, but cancelled and changed to Windows 2003.
 * There is an secret theme named "SmallAeroTest", maybe this is Aero support test for 128 MB Cards.
 * It meaned to release on late 2002, but there are some problems with releases, release begin longer, and longer, and has been released in 10.04.2003
 * It meaned to release Service Packs, but no SP are released. Source "Microsoft Plans of 2004-2007"
 * BTW, Service Pack 1 Beta 1 and 2 are only released Service Packs Ever. Official SP 1 Beta 1(3098.03sp.beta1-1130.030611-2311), Official SP 2 Beta 2(3098.03sp.beta2-1623.030730-1140)

Best updates for Windows 2003

 * KB030501 - Security Update (For Final, 01.05.2003)
 * KB061111 - Windows Defender Install Update (For Final,Professional/Home, 11.11.2006)
 * KB091011 - Internet Explorer Update 8.0 (10.11.2009)
 * KB050505 - Windows LDDM/WDDM Driver package (05.05.05)
 * KB050605 - Windows Aero (Fully working from Vista Beta 2 - 06.05.05)
 * KB100101 - Final Technical update for all editions of Windows 2003 (01.01.2010)

Between Longhorn and 2003.
There are rumors, it meant to be some elements, or all project has to be moved to 2003.

Only one file exists from longhorn. From 3683 sidebar.dll (Made 01.01.2003)