Watch out: Windows 10 KB40387821 wipes out your apps and programs

By: Madeleine Dean
2 minute read
KB40387821 bugs

Windows 10 KB40387821 is a mysterious cumulative update that wreaks havoc on computers, with users reporting all of their apps and programs deleted except for Windows Defender. And although the antivirus is still available, it won’t update.

Here’s how one use describes this problem on Microsoft’s forum:

Windows 10 Home updated to version 1703 on Sept. 17th. It wiped out ALL my programs except Windows Defender. But Defender will now scan but won’t update, neither automatically nor manually. New definitions occurred 6 days ago either. Error Ox80004004. It says “connection failed”, but my internet connection is fine. No other competing virus protection is installed. How do I fix this?

Where did KB40387821 come from?

Strangely enough, KB40387821 is not listed in Microsoft’s Update Catalog. The Windows 10 Update History page doesn’t mention anything about it, either. However, users report that Microsoft deployed this update last week and, unfortunately, it brings issues of its own.

As stated above, many Windows 10 Creators Update users reported this update wipes out all their programs. Moreover, after the OS installed this update, Windows 10’s Update History no longer lists the updates previously installed.

Windows Update KB40387821 installed 9-18-17 and I lost ALL my programs. It too all the “fun” out of “function”. The update took over my pc. NO programs nor updates are listed before 9-16-17.

KB40387821 is likely an upcoming cumulative update that wasreleased too early. If this update broke your PC, try uninstalling it and then restarting your computer. If this solution doesn’t fix the problem, perform a system restore or reinstall Windows.

If you’ve encountered any other issues after installing KB40387821, tell us more about your experience in the comment section below.

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