Article ID : 00010542 / Last Modified : 08/15/2015

Error 643 or 646 Windows update failed to install important updates.

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You may receive this error when trying to install the following updates:

  • Microsoft® .NET framework 1.1 SP1
  • Security Update for Microsoft .NET Framework, Version 1.1 Service Pack 1 (KB928366)

Follow the procedure below to resolve the issue:

  1. Use the Windows Installer CleanUp Utility to remove the Microsoft .NET Framework software.
  2. Restart the computer.
  3. Download and install the following software from the Microsoft Web site.
  4. Run Windows Update to install the Security Update for Microsoft .NET Framework, Version 1.1 Service Pack 1 (KB928366).