Microsoft Windows beta builds previously leaked & later lost

Thank you for your work on archiving and documenting computer programs here on the LMW forums. I suggest that exact sources be placed though. It may turn out that a lot of these builds never leaked at all, or don't even exist.

Here is another list of builds that were presumably leaked by Warez groups or other sources back in the day before they went lost or were mentioned on Warez CD lists, this time focusing on the Windows NT family of operating systems.

These builds are as follows:

Windows NT 3.1 PDK 1 IDW 15 build - The National Museum of American History supposedly has a disc containing this build.

Windows NT 3.1 April 1992 build - On 7 October 2018, a picture of this build's discs were posted on BetaArchive by member ReflectiaX. Based on the date on the PDK disc, the build number is likely between 250 and 270, and it might be one of the builds referenced in the source code of Windows NT 3.5 build 782.1 or Windows NT 4.0. The build itself remains unleaked for now.

Windows NT 3.1 build 254 - On 12 March 2019, a disc scan of this build was posted on the BetaArchive Discord by member ReflectiaX.

Windows NT 3.5 build 807.1 (pre-release) - This build was found in an unknown Warez release.

Windows NT 3.51 build 993.1 - This build is listed in warez lists for three different warez compilation CDs - Ganja 6, Voodoo 3 and Razor 04. Based on the file dates, it was compiled before 1995-04-16, probably around 1995-04-01. The build itself hasn't been found yet.

Windows NT 3.51 build 1037.1 - This build is listed on a Greek warez CD (PC26_95), as well as the Who 6 CD. It was apparently leaked in both Server and Workstation editions by the warez group PWA. Its existence is yet to be confirmed.

Microsoft Cairo build 297.1 - On 16 August 2018, a disc scan of this build was posted on BetaArchive by member ReflectiaX.

Windows NT 4.0 build 1124.1 - This build is listed in old warez lists, but the build hasn't been found.

Windows NT 4.0 build 1201.1 - This build is referenced in the Fate volume 18 warez cd list but hasn't been found yet and thus can't be confirmed to exist.

Windows NT 4.0 build 1293.1 - This build is referenced in the Enigma Utils volume 1 warez CD and Fate volume 66 warez CD lists but hasn't been found yet and thus can't be confirmed to exist.

Windows NT 4.0 build 1326.1 - This build is listed on the Total Utils 23 warez CD. One part of what is labeled as this build was recovered, but the folder inside is named "NT1313", so it's currently impossible to determine which build it actually is. This build hasn't been found yet.

Windows NT 4.0 build 1332.1 - A copy labeled as build 1332 was found in an unknown warez release, but the files inside turned out to be Windows 95 build 1107. The actual build 1332.1 hasn't been found yet.

Windows 2000 build 1516.1 - This build is listed in Total Utils 74 warez CD as well as Fate 263, but hasn't been found yet and thus can't be confirmed to exist. 1515 was also mislabelled as 1516 at some point.

Windows 2000 build 1580.1 - The Workstation edition is listed in the Fate 319 warez CD list, but the build hasn't been found yet.

Windows 2000 build 1645.1 - This build is listed in the Fate 371 and Total Utils 121 warez CD lists, but the build hasn't been found yet.

Windows 2000 build 1661.1 - This build is listed in the Fate 381 warez CD list, but the build hasn't been found yet.

Windows 2000 build 1717.1 - This build is listed on the Fate 466 warez CD and was supposedly leaked by the warez group called PWA, but the build hasn't been found yet. Files from this build can also be seen in a few Windows Me builds.

Windows 2000 build 1723.1 - The Workstation edition of 5.0.1723.1 was scene leaked by group PWA, but hasn't been found yet.

Windows 2000 build 1816.1 - This build, as well as its Driver library and Resource kit, are listed in the Fate 621 warez CD list, but the build hasn't been found yet.

Windows 2000 build 1996.1 - It was apparently scene leaked by the warez group PWA on 10 March 1999, but hasn't been found yet and thus can't be confirmed to exist.

Windows 2000 build 2136.1 - On 9 September 2020, a picture of the CD was posted on the BetaArchive Discord by member ReflectiaX. He then later obtained said disc a couple days later.

Windows XP build 2442 - This build is mentioned in various posts on the Chinese Software Developer Network (CSDN), including a thread about installing drivers for a modem from May 2001, or two threads about timebomb removal from July 2001, meaning this build was likely leaked online between its compile date (17 February 2001) and the date of the first post (22 May 2001). As of 2021, this build hasn't been leaked to the public. BetaWorld claims to have a copy of this build, but they chose not to share it. On 20 October 2020, BetaWorld user by the name of MacAdmin uploaded a picture of a Chinese warez CD called "KEE-044" containing the build. On 24 October 2020, BetaWorld user by the name of 随便问我 uploaded a higher-resolution picture of the same CD. It is currently only available to select BetaWorld members.

Windows XP build 2600.1060 (Service Pack 1 Build) - Several screenshots of this build have been shown. Czech technology news site Zive had posted an image of this build. Many sources used to hold this build, but most of them have been long shut down. As of 2021, the build itself remains unleaked.

Windows XP build 2600.1097 (Service Pack 1 Build) - Multiple sources used to hold this build, but most download sources have been long gone. PlanetXP.de formerly also had several screenshots of the build but the website has been shut down since 2004. As of 2021, it remains unleaked.

Windows XP build 2600.1102 (Service Pack 1 Build) - Several screenshots from likely an ieXbeta member were leaked. WindowsPro.net also used to have downloads to this build but the website has been down for a long time. As of 2021, the build itself remains unleaked.

Windows XP build 2600.2178 (Service Pack 2 Build) - ReflectiaX showcased multiple Burnlab discs on 22 September 2018 on the BetaArchive Discord, with one of the discs having this build.

Windows Server 2003 build 2499 - The beta-scene member KenOath claimed to had a copy of this build but had chosen not to share it.

Windows Server 2003 build 3676 - This build was formerly found on WinBeta and WinFuture.de formerly had screenshots of the build, but they were deleted without any archived versions. KenOath shared a few screenshots of this build on BetaArchive.

Windows Longhorn build 3663 - A rumor exists that the build was leaked in the far past, but due to the low interest, the download links were permanently removed. There is no evidence to support this rumor, however, and it can be safely assumed that there was never any leak beyond a few screenshots.

Windows Longhorn build 4050 (private/lab06 demo.031018-2015) - Somehow xBetas.com got a hold of this build and added their own "touch", as this build was supposedly shown at PDC 2003.

Windows Longhorn build 4050 (private/lab06 demo.031020-1959) - The files for the Sticky Notes component of this build were leaked by ReflectiaX on 10 October 2020.

Windows Longhorn build 4050 (private/lab06 demo.031022) - On 2018-09-27, BetaArchive member ReflectiaX claimed to have this build.

Windows Longhorn build 4089 - In the BetaArchive topic "New Longhorn builds for a new decade" by Grabberslasher on 23 January 2020 where more than 35 Longhorn pre and post-reset builds were leaked, including all then-unleaked builds showcased on UX.Unleaked, ReflectiaX mentioned that he once had a copy of this build, or at least another 4089 numbered build, but had since lost it.

Windows Vista build 5221 (vbl ux dev checkin gamesux) - Unfortunately, the demo that originally showed this build was taken down and no archived versions exist at this time.

Windows Vista build 5268 - This build was presumably released to OEM testers in December 2005 for the Community Technology Preview.

Windows Vista build 5342 (vbl ux partners winapps) - This build was released to technical beta testers and to certain corporate customers after extensive feedback from the earlier Febuary Community Technology Preview (CTP) release. According to Wikipedia, this build did not meet CTP quality standards and was only released in the Ultimate edition. This build isn't leaked, but there is a better-known compile of it which has the build string 5342.2.winmain_idx04.060321-1730, dated a few days after this one. Build 5342.2 is not overly different from 5308, note, and the screenshot used in the build infobox is of that compile. Note that the sidebar (in particular the clock widget) is slightly different from in the final version.

Windows Vista build 5442 - It is one of two builds that were demonstrated as non-genuine by Raiker, the other is build 5476.

Windows Vista build 5476 - It is one of two builds that were demonstrated as non-genuine by Raiker, the other is the above mentioned build 5442.

Windows 8 build 7930 - Only one alleged screenshot of this build's Windows Update Control Panel applet was leaked on the Chinese website Win7China, attributed to Russian leaker Zukona (who presumably has or had a copy of the build).

Windows 8 build 7971 - This build was released on Microsoft Connect to OEM partners. Some fake versions of this build were rumorly formerly available (likely rumored to be spammed out by Microsoft employees as a trolling scheme to Warez & Piracy groups).

Windows 8 build 8011 - some fake versions of this build were formerly available (likely rumored to be spammed out by Microsoft employees as a trolling scheme to Warez & Piracy groups).

Windows 8 build 8112 - A Microsoft Windows Web Installer has a setup version of this build and would've downloaded a Microsoft Windows Developer Preview Upgrade for this build, however, it installs build 8102.101 instead.

Windows 8 build 8437 - It was supposedly leaked on the Chinese website BetaWorld, but at the moment this cannot be confirmed or refuted as it's not publicly available. As of 2021, it remains unleaked.

Windows 8.1 build 9403 - According to news sources from that time, it was released to partners on around 27 May 2013. Supposedly development of most of the Metro apps bundled with Windows 8.1 was already finished at that point and Microsoft was waiting for feedback to fix any bugs before getting the public preview ready.

Windows 8.1 build 9447 - A screenshot was found on an eBay listing of a prototype Nokia Lumia 2020 "Illusionist" tablet, which has since been sold.

Windows 8.1 build 9468 - One screenshot was found on the Chinese website BetaWorld. They may have this build, but this cannot yet be confirmed or deprecated as it is not publicly available. It remains unleaked as of 2021.

Windows 8.1 build 9477 (fbl partner out21) - One screenshot was found on the Chinese website BetaWorld. This build is currently only available to select BetaWorld members. They may have this build, but at the moment this cannot yet be confirmed or deprecated as it is not publicly available. As of 2021, it remains unleaked.

Windows 8.1 build 9478 - One screenshot was found on the Chinese website BetaWorld. They may have this build, but this cannot yet be confirmed or deprecated as it is not publicly available. Russian website PC Portal also showed a screenshot with the tag of this build. It remains unleaked as of 2021.

Windows Server 2016 build 10513 - Multiple files from this build have been found from part of a RemoteIE server, and are available to download.

Windows 10 build 16232.1004 - This build was released to Windows Insiders in the Fast Ring on 6 July 2017. It only updated the version number of Notepad.exe. This build is now currently lost, as it is no longer available for download.

Windows 10 build 17662 - A Windows Update picture showing this build as a pending download was found at an ASUS support website about the May 2019 Update features.

Windows 10 build 17706 - A screenshot from a pending Windows Update restart was shown by a Microsoft employee on 28 June 2018.

Windows 10 build 18300.1000 - A screenshot of a pending restart was shown by a Microsoft employee on 10 December 2018.

Windows 10 build 18882.1000 - A screenshot of a pending restart was shown by a Microsoft employee on 19 April 2019.

Windows 10 build 18943 - It was mentioned between July 2019 and January 2020 as the minimum build to download the Microsoft Store Notepad before build 19016.

Windows 10 build 19500 - It is mentioned in the system requirements for Windows 10X build 19563's Microsoft Emulator image.

Windows 10 build 19615 - A comment about this build was posted by a Microsoft employee on 2020-05-01. It's labeled as an Insider build but it was never actually released.

Windows Server build 19504 - Screenshots of downloads related to this build were leaked on Twitter on 26 October 2019.

Sources I've used are BetaWiki & the BetaArchive wiki once again. Many of these builds aren't confirmed yet or aren't likely to exist for now, but I just wanted to put a list for this forum.

Warez means software that has been illegally copied and made available.

Many of these Microsoft Windows builds were leaked back in the late-1990s to early-2000s by various warez groups, but were later lost likely due to these groups being shut down or being raided by government officials.