Error 0x80070643
Fatal error during installation
This is the same fatal-install failure as 1603, shown in hexadecimal. It appears both in Windows Update and in ordinary installers, and the fix depends on which of the two you are looking at.
What it actually means
The code maps to the same underlying condition as MSI error 1603. Windows Update reports it in hex, which is why the same problem appears under two different codes and why advice for one often does not match the other.
How to fix it, in order
Ordered by how often each one is the answer, not by how clever it sounds.
- 01If it came from Windows Update, run the Windows Update troubleshooter first: Settings, System, Troubleshoot, Other troubleshooters.
- 02For the recovery-partition variant that appeared with the January 2024 update, the cause is a WinRE partition too small to patch. Microsoft published a specific procedure for resizing it; general 1603 advice will not help.
- 03If it came from a normal installer, treat it exactly as error 1603: uninstall any existing version, run as administrator, check disk space, then read the verbose log.
- 04Run "sfc /scannow" followed by DISM if the failure repeats across different installers, which points at damaged system files rather than at the package.
Windows Update and installers are different problems
The same code covering both is why so much advice contradicts itself. Establish which one you have before following any guide: an update failure and a package failure share nothing beyond the number on screen.
Common questions
- Is 0x80070643 the same as error 1603?
- Yes, it is the same fatal installation failure expressed in hexadecimal. Windows Update reports the hex form while Windows Installer reports 1603.
- Why does Windows Update keep failing with 0x80070643?
- Run the Windows Update troubleshooter first. If it relates to a recovery environment update, the cause is usually a WinRE partition with too little free space, which needs the specific resizing procedure rather than generic installer advice.
Before you retry the installer
If the package came from anywhere other than the publisher, confirm it is the file they actually shipped. Check its SHA-256 against our index, which settles in seconds whether you are debugging an installer or a damaged download.