Recently after a dirty shutdown one server kept displaying the familiar “Why did the computer shutdown unexpectedly” for all users, at every logon.
Usually a reboot resolves this, but did not. I have heard of this happening over the years due to specific updates, but no updates had been applied recently. Ultimately it required locating the registry key which contains the flags to initiate the popup; \HKLM\Software\Microsoft\Windows\CurrentVersion\Reliability and deleting any subkeys referencing the last event, such as “DirtyShutdown”. These keys get recreated after the next event. Changing values from 1 to 0 will stop the popup, but this disables it all together. Not a good idea. Of course; make sure you backup the registry before doing so and do not make changes to the registry if you are not familiar with doing so.