I've seen this on two machines now - once when performing a manual upgrade using the ISO and once via WSUS.

Both times, the installer gets to 73%, then stays there - indefinitely.

On the manual installer, I can just click Cancel and after a short while, the installer disappears and I'm back at the desktop. But when installing via WSUS, there is no cancel button. I wonder if it's safe to restart the computer, or will that completely bork Windows??

Is there a log file for the 1809 update that I can take a look at to figure out what's going wrong on these two PCs?


The setupact.log in the %windir%\Panther folder is what you want to review to see what may have happened during the install. There might also be a $Windows.~BT folder. If there is, look for the setupact.log there.

Given where you are in the install process, I'd guess there's a device driver or something along those lines that causing the delay.

  • Thanks for the tip. I came across this article (support.microsoft.com/en-gb/help/927521/…) which mentions the same Panther folder and setupact.log file. C:\$WINDOWS.~BT\Sources\Panther\setuperr.log is also a very interesting file for diagnosing setup errors. – Matty Brown Feb 5 '19 at 16:18
  • Setuperr.log is a parse of some of the errors found in the setupact.log but it lacks the context. Its nice to use as a starting point but if you're looking to root cause an issue, keep with setupact.log – Joseph Conway Feb 6 '19 at 17:03

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