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Python setup error 0x80070643 is a Windows Installer (MSI) failure. The form 0x8007643 is probably a shortened or mistyped display of the same code. It can appear while Python is being installed, repaired, upgraded, or removed; it is not a Python traceback and does not identify one universal cause.
The most reliable repair is to identify the action that failed, run Microsoft’s Program Install and Uninstall troubleshooter against the Python entry, restart Windows, and then reinstall Python through its official Windows installation route. Keep the installer log if the problem continues, because the failed MSI action determines what should happen next.
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What the error means
Windows Installer uses hexadecimal status codes to report failures while processing an MSI package. Python’s Windows installer can use MSI packages for per-user or per-machine setup, maintenance, upgrades, and removal. When the MSI transaction cannot complete, setup may show a message such as “Failed to install MSI package” or “Failed to configure per-machine MSI package.”
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Identify the exact situation first
Before removing anything, write down these details:
- Python version shown by the installer.
- Windows edition and version.
- Whether you were installing, repairing, upgrading, or uninstalling.
- Whether the installation was intended for one user or for all users (per-machine).
- Whether Python appears in Windows Installed apps or in Programs and Features.
- The exact MSI log lines containing the failure.
Do not assume that a failed upgrade means the existing interpreter is unusable. If a previous version still launches, leave it in place until you have recorded the version and the failed action. Avoid deleting Python folders or registry entries simply because they look old; doing so can remove the metadata that Windows needs to complete an uninstall.
Use Microsoft’s supported repair tool
1. Start the Program Install and Uninstall troubleshooter
Microsoft’s Program Install and Uninstall troubleshooter is designed for desktop programs that cannot be installed, updated, or removed. Microsoft says it can address corrupted registry keys, corrupted update data, incomplete uninstall information, and blocks that prevent a desktop program from being installed or uninstalled.
- Obtain the Program Install and Uninstall troubleshooter from Microsoft Support and start it.
- Choose the activity that matches your failure: installing or uninstalling. Use the uninstall path when a stale Python entry is preventing removal or an upgrade.
- Allow the tool to detect installed products, then select the Python entry related to the failed operation.
- Apply the recommended correction and let the tool finish. Record any product name or identifier it reports.
- If Python is not listed, follow the tool’s prompt for a product code from the MSI package. Do not guess a code or select an unrelated program.
The troubleshooter repairs installer state; it does not install Python for you. When it reports that the correction is complete, close it normally rather than deleting additional files by hand.
2. Restart Windows
Restart after the troubleshooter has changed installation state. A restart releases pending file operations and reloads Windows Installer services, but it is a transition step, not a guaranteed fix by itself. After Windows starts, check whether the Python entry is still present and whether the original operation can be repeated.
Install Python again through the official Windows route
Python’s Windows documentation explains that Windows does not include a system-supported Python installation. It directs users to the Python Install Manager or another supported Python distribution and documents installation scope, PATH behavior, supported Windows versions, and troubleshooting.
Choose the installer deliberately
- Use Python’s official Windows documentation to select the current supported installation channel rather than a repackaged executable from an unknown site.
- Match the package architecture to Windows and to any applications that will load Python or its extension modules.
- Decide whether the installation should be per-user or per-machine. A per-machine installation changes system-wide state and is the context in which logs commonly refer to a “per-machine MSI package.”
- Review the PATH choice and other installer options before confirming setup. Do not assume that an older PATH entry will be corrected automatically.
Run the installation as a clean test
- Close Python shells, editors, terminals, and any program that may be using the old interpreter.
- Start the official installer or Python Install Manager selected in the documentation.
- Choose the intended scope and architecture, then proceed without changing unrelated settings.
- If setup offers repair, modify, or remove for an existing entry, use the option that matches your recorded goal instead of starting several competing installers.
- Let the operation complete and note the final result. If it fails again, preserve the new log before attempting another change.
A successful installation should leave a recognizable Python entry in Windows’ installed-program list and make the selected interpreter available according to the PATH and scope choices you made. If another version remains installed, verify which interpreter your application is actually invoking before removing it.
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| Original action | What to check | Next supported move |
|---|---|---|
| New installation | Whether another Python version or an incomplete entry already exists | Use the troubleshooter for a conflicting or incomplete entry, restart, then retry the official installer |
| Upgrade | Whether the older Python entry remains and whether the log names a per-machine package | Repair the older entry with the troubleshooter before attempting the upgrade again |
| Repair or modify | The exact feature or MSI action that failed | Keep the log, run the troubleshooter against the affected entry, then repeat only the intended maintenance action |
| Uninstall | Whether Python is listed in Installed apps or Programs and Features | Use the troubleshooter’s uninstall path; if the entry is missing, use the MSI product code when the tool requests it |
This comparison is a decision aid, not a set of interchangeable commands. The same status code can arise from different installer states, so an install failure and an uninstall failure should not be handled identically.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Read the MSI log when the problem returns
If the same error appears after the troubleshooter, restart, and an official reinstall attempt, stop repeating the installer blindly. Preserve the complete MSI or Python setup log, including the lines immediately before and after the failure. Record:
- The Python release and installer channel.
- The Windows version and installation scope.
- The MSI package name or product code, if shown.
- The first failed action, not merely the final summary line.
- Whether the failure occurred while copying files, configuring a feature, registering a product, or removing an existing product.
The final message may only say that the MSI package failed. Earlier lines usually identify the operation that Windows could not complete. That distinction matters when seeking help or deciding whether the next attempt should be a repair, uninstall, or fresh installation.
What not to do
- Do not delete arbitrary registry keys. Microsoft’s supported workflow targets the specific corrupted entries and uninstall data it detects. Manual deletion can make the product impossible to remove cleanly.
- Do not remove every Python directory as a first step. Files left behind may be user data or a working installation, while deleting them does not necessarily remove MSI registration.
- Do not run random msiexec commands copied from unrelated errors. There is no evidence-backed universal command for this Python status code; an incorrect product code or switch can alter the wrong installation.
- Do not install several Python packages at once. Multiple installers can leave you unsure which entry, PATH setting, or interpreter is being tested.
- Do not treat the code as proof of malware. It is an installer status, not a security diagnosis.
When the repair is complete
Confirm the result using the task you originally needed:
- For an installation, launch the intended Python interpreter and verify that the expected version is selected.
- For an upgrade, verify that the new version is the one your application or terminal resolves, while documenting any older version you intentionally retained.
- For an uninstall, confirm that the Python entry is gone from the relevant installed-program list and that no application still depends on it.
- For a repair, repeat the feature or action that previously failed and keep the successful log with your installation notes.
If the operation still fails, provide the preserved log and the recorded Windows, Python, scope, and action details to the administrator or support channel handling the system. Those facts are more useful than trying increasingly destructive cleanup steps.
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