Windows 10's forced cumulative update (KB3081424) causing endless reboots, but there is a solution
Forcing updates on all users must have seemed like a good idea in the Windows 10 planning meetings -- no more PCs at risk from unpatched vulnerabilities -- but already the mandatory updates are causing major headaches for many users.
Even before Windows 10 officially launched, there was an update (KB3074681) that caused crashes in File Explorer, and NVidia driver updates that were breaking some people’s computers. Last week’s servicing rollup fixed various bugs and issues, but for some users it actually caused their PCs to go into a reboot loop.
The problem is the cumulative update, KB3081424, is failing to install properly on some computers. Affected users report that after the update downloads, it requests a reboot to install, then gets part way through the installation, reboots, continues and gets a little further, reboots again, announces there’s a problem, rolls things back, then reboots once more. And because updates are mandatory, the process starts all over again.
While Microsoft has released a tool that you can use to block bad updates, it doesn’t seem to work in this case. Fortunately there is a workaround.
The problem appears to be caused by the failed install writing a bad entry to the Windows registry, and this, in turn, prevents the update from installing the next time it tries. To get around this issue you have to delete some registry keys.
Click Start, type regedit, and hit enter to launch the Windows registry editor.
You should backup the registry before proceeding, just in case making the following changes causes you problems. Highlight ProfileList, right-click, select Export and enter a backup name.
Once backed up, navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
With that done, Scan through the ProfileList IDs. Ignore the ones ending in 18, 19, and 20. If you have two or more entries starting with S-1-5-21, then this fix may work for you. If you only have one entry that begins with S-1-5-21, then this fix won't work, and you'll have to try something else. Click on ProfileImagePath for each of the S-1-5-21 entries, and look for users that no longer exist in the registry. If you're not sure which users are valid, click Start, type Computer Management and hit enter. Under Local Users and Groups browse the list of Users. Delete any of the S-1-5-21 keys which shouldn't be there. As with any registry editing, make sure you only delete something if you're comfortable it's safe to do so.
Close regedit and reboot.
Afterwards (or instead of) you can try manually installing the update from:
You can find out more about the error, and possible solution here.