Credits

Legacy Update was started and is primarily developed by Adam Demasi (@kirb), with contributions from:

The Legacy Update program source code is licensed under the Apache License, version 2.0. Refer to LICENSE.md.

Legacy Update NT is built thanks to the great research and documentation on Windows NT 4.0 updates by ZCM Services, Bear Windows, MDGx, and members of MSFN.

We make use of some portions of the Windows SDK, MinGW-w64, and NSIS.

Thanks to the Internet Archive for all they do to preserve information that might otherwise be lost forever. Their extensive Wayback Machine backups of the Windows Update website are what allowed me to successfully create Legacy Update.

Thanks to the countless people on MSFN, BetaArchive, and other Microsoft fan forums for all the little tidbits that helped me get this working.

A very special thank you to those who support me on Ko-fi, GitHub Sponsors, and Patreon, and to those who report bugs and help me discover fixes.

Disclaimer

This service is not affiliated with or endorsed by Microsoft. This software is provided “as is”, without warranty of any kind. We don’t believe anything should go wrong, but please ensure you have backups of any important data anyway.

Acknowledgements

Legacy Update is made possible thanks to the following open source projects.

jQuery

Copyright (c) 2010 John Resig, https://jquery.com/

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

MinGW-w64

With exception of certain parts that are prominently marked as being in the Public Domain, BSD, or LGPL this Software is provided under the Zope Public License (ZPL) Version 2.1.

Copyright (c) 2009 - 2013 by the mingw-w64 project

See the AUTHORS file for the list of contributors to the mingw-w64 project.

This license has been certified as open source. It has also been designated as GPL compatible by the Free Software Foundation (FSF).

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  1. Redistributions in source code must retain the accompanying copyright notice, this list of conditions, and the following disclaimer.
  2. Redistributions in binary form must reproduce the accompanying copyright notice, this list of conditions, and the following disclaimer in the documentation and/or other materials provided with the distribution.
  3. Names of the copyright holders must not be used to endorse or promote products derived from this software without prior written permission from the copyright holders.
  4. The right to distribute this software or to use it for any purpose does not give you the right to use Servicemarks (sm) or Trademarks (tm) of the copyright holders. Use of them is covered by separate agreement with the copyright holders.
  5. If any files are modified, you must cause the modified files to carry prominent notices stating that you changed the files and the date of any change.

Disclaimer

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

NSIS

Copyright (C) 1999-2025 Contributors

More detailed copyright information can be found in the individual source code files.

APPLICABLE LICENSES

SPECIAL EXCEPTION FOR LZMA COMPRESSION MODULE

Igor Pavlov and Amir Szekely, the authors of the LZMA compression module for NSIS, expressly permit you to statically or dynamically link your code (or bind by name) to the files from the LZMA compression module for NSIS without subjecting your linked code to the terms of the Common Public license version 1.0. Any modifications or additions to files from the LZMA compression module for NSIS, however, are subject to the terms of the Common Public License version 1.0.

NSxfer

The zlib/libpng License
Copyright (c) 2014-2026, Marius Negrutiu

This software is provided 'as-is', without any express or implied warranty.
In no event will the authors be held liable for any damages arising from the use of this software.

Permission is granted to anyone to use this software for any purpose, including commercial applications,
and to alter it and redistribute it freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.

  2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.

  3. This notice may not be removed or altered from any source distribution.

PIE

Copyright 2010 Jason Johnston

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.