ERROR_PATCH_TARGET_NOT_FOUND - 1642 (0x66A)
The upgrade cannot be installed by the Windows Installer service because the program to be upgraded may be missing, or the upgrade may update a different version of the program. Verify that the program to be upgraded exists on your computer and that you have the correct upgrade.
Updated: Feb 21, 2026
Technical Meaning
The error code ERROR_PATCH_TARGET_NOT_FOUND with the numeric value 1642 and hexadecimal representation 0x66A indicates that a required program or file necessary for an upgrade process is missing. This can occur when attempting to apply updates, patches, or service packs to a Windows installation.
Error Details
This error typically arises in scenarios where the installer service expects a specific version of a program but cannot locate it on the system. The message suggests that either the targeted application has been removed or replaced with a different version, which is incompatible with the upgrade being attempted.
Usage Context
The ERROR_PATCH_TARGET_NOT_FOUND error can be encountered during various Windows update processes, including:
- Applying service packs
- Installing cumulative updates
- Executing hotfixes
- Upgrading applications through Windows Update
Developer Interpretation
Developers should interpret this error as an indication that the upgrade process cannot proceed due to a missing or incompatible target application. This can affect both system and application upgrades, leading to incomplete installations or failed update processes.
Related Errors
ERROR_FILE_NOT_FOUND(2)ERROR_PATH_NOT_FOUND(3)ERROR_BAD_EXE_FORMAT(1114)
FAQ
Q: What does the error code 1642 mean?
A: The error code 1642, 'Patch Target Not Found', indicates that a required program or file is missing during an upgrade process.
Q: How can I resolve this issue?
A: Ensure all necessary programs and files are present on the system before attempting the upgrade again. Verify that no conflicting updates or patches have been applied.
Summary
The ERROR_PATCH_TARGET_NOT_FOUND error (1642) is a generic indication that an upgrade process cannot proceed due to missing or incompatible target applications. Developers should ensure all necessary components are present and compatible before attempting upgrades.