Windows 10 KB4549951 causes losing files

KB4549951 is a routine cumulative update in April 2020, which is mainly applicable to Windows 10 Version 1903 and Version 1909.

However, this update has previously been revealed that there are multiple problems such as the blue screen of death, WiFi outage and abnormal Bluetooth driver, and even the loss of personal files.

Unfortunately, until now, Microsoft has not confirmed this problem, and the more users who update it, the more users who have lost personal files and feedback to Microsoft.

The system installation, update, and upgrade will lose the user’s personal files and appeared in Windows 10 Version 1809 version at the earliest. At that time, Microsoft directly announced the withdrawal of this version.

Although Microsoft has fixed this problem and re-released the new version later, it seems that there are still very similar problems in the latest version.


KB4549951 and previous cumulative updates have lost users’ personal files. The main reason is that Microsoft had some unexpected failures during the upgrade process.

According to Microsoft, when the system is installed and updated, the user’s personal files will be moved to other directories for backup, and the user’s personal files will be restored after the upgrade is completed.

In fact, this kind of problem has not been lost recently, but the system cannot restore the backup user’s personal files normally during the installation phase.

The user’s personal files (all directories under C:\USER\) are not deleted directly but become backup files ending in .ooo or .bak hidden in a certain location.

It has lasted more than 15 days from the user who initially reported the problem to the latest feedback. Unfortunately, Microsoft has not confirmed that the problem does not exist to be fixed.

But the hard-working Windows 10 users have already figured out the solution themselves, and only need to constantly restart to allow the system to restore the backup files.

According to users in the feedback community, if the latest cumulative update can be directly uninstalled to restore files, in theory, as long as the system is uninstalled, the backup and restore steps will be re-operated.

At the same time, the user can also restart the system continuously. After testing, the user restarts about 6 to 8 times, and all files in the C:\USER\ directory can also be automatically restored.