A cumulative update is a Windows update that contains a bunch of previous updates bundled as one. It's useful when you haven't updated in a while because it lets you jump to a certain Windows milestone (like the Anniversary Update) without installing those past updates one by one.
Unfortunately, cumulative updates can be tricky as evidenced by Cumulative Update KB3189866, which, according to user reports, can get stuck at numerous points throughout the update process -- namely at 45%, 46%, 48%, 49%, and 95%.
If you're trying to install this cumulative update but progress keeps halting at one of those percentages, there are three potential fixes you should try. Go at them in this order:
- Run the Windows Update Troubleshooter -- This is always the first step you should take when trying to resolve problems with Windows Update. Access it by searching the Start Menu for Troubleshooting, then under System and Security, click Fix problems with Windows Update.
- Clear the SoftwareDistribution folder -- You can find this directly inside the C:\Windows folder (or whichever drive to which you installed Windows 10). Simply select all of the files in the SoftwareDistribution folder and delete them.
- Download the update directly -- Through the Microsoft Update Catalog, you can manually download the setup files for various Windows updates. In this case, download the one for KB3189866 and run it: 32-bit installer and 64-bit installer.
If none of those steps work, feel free to leave a comment down below and let us know what kind of errors you're running into. If one of the steps do work, please let us know which one!