Microsoft releases a monthly cumulative update to Windows every second Tuesday of a month, dubbed "patch Tuesday," however sometimes the company has the updates ready to go before that date, and puts them out as Update Previews. These are not "beta" versions of a software update, but contents of the upcoming patch Tuesday just being released ahead of its time, and as such it's offered even to regular users that aren't Insiders. One such update preview for the month of October 2024 is horribly broken.

Dubbed the Windows 11 Update Preview KB5043145, and released on September 26, this update is found by users to cause blue screens of death (BSODs), and send the system into "boot loops"—a condition where the OS fails to load, causing the machine to reboot over and over again, until you can boot with a recovery disc just to boot into your existing installation. The KB5043145 update preview has since been pulled, although it's still part of the Microsoft Update Catalog, a repository that holds all Windows Updates as standalone installers.