A Windows update failing once can be temporary. If the same update keeps failing, however, repeating the installation without learning anything new is less useful than finding out why it failed.
Start with the error code shown by Windows Update. Microsoft documents different Windows Update codes separately because they can represent very different problems. For example, some codes mean Windows is missing required files, some indicate damaged servicing data, some point to insufficient storage, and others indicate a connection or permissions problem. [R1][R2]
The error code is therefore evidence. It is not just a generic “update failed” message.
Check whether Windows is waiting for a restart
Some updates cannot finish until Windows restarts.
Microsoft's Windows Update troubleshooting guidance says that if the computer did not restart after a previous update, pending actions may still need to finish before new updates can be applied. [R3]
Before trying more invasive repairs, check Settings → Windows Update for a restart request. Restart the PC normally, return to Windows Update, and check whether the same update still fails.
A restart does not fix every update problem, but it can complete work that Windows was already waiting to finish.
Check free space
Windows needs working space while downloading and installing updates.
Microsoft says a PC that is running out of storage may have trouble installing Windows updates. Windows also checks available storage before installation and can ask you to free space if there is not enough. [R4]
If Windows reports a storage-related error, free space first rather than repairing unrelated update components.
Use Windows' own Storage and Cleanup recommendations tools to identify removable data. Do not manually delete Windows system folders just because they appear large.
The Windows component store may need repair
Windows keeps system components used for servicing and updates in a component store.
Microsoft documents several update errors that can result from missing or damaged component-store files. Its servicing tools can scan that store for corruption and repair it. [R2][R5]
This is different from simply downloading the update again. If the files Windows relies on to service the operating system are damaged or missing, the servicing state itself may need repair before the update can install successfully.
The exact error matters here. Do not assume every repeated update failure means the component store is corrupt.
Check the connection path
Windows Update also depends on reaching Microsoft's update services.
Microsoft documents update failures caused by timeouts, firewalls, proxies, and other connection problems. [R2]
If the error points toward connectivity, check whether the PC has normal internet access and whether a VPN or proxy is changing the connection. Repairing system files will not solve a blocked update connection.
Should Windows Update be reset?
Windows Update has working folders and services that can themselves become part of a failure.
Microsoft provides procedures for resetting Windows Update components, but those procedures stop update-related services and rename or remove update working folders such as SoftwareDistribution and catroot2. Microsoft also recommends trying the Windows Update troubleshooter before a manual reset. [R6]
That makes a reset a repair step, not a routine first response to every failed update.
If Kajlos proposes this repair, it should do so because the evidence points toward Windows Update's local state, not simply because an installation failed.
How do I know the problem is fixed?
After the suspected cause has been addressed, run Windows Update again and check the same update.
The repair is successful when that update installs and Windows no longer reports the original failure. If it fails again, compare the new error code with the previous one rather than assuming nothing changed.
A repeated update failure is not one problem with one universal fix.
The useful question is:
What is preventing this particular update from completing on this PC?