How to Fix Windows Update Error Code C8000266

To keep Windows functions at an optimal state, constant system updates are a must-do. Known as Windows Update, the process of essentially bringing all systems up-to-speed and up-to-date should be done regularly.

What does Windows Update do? This is an essential service that, when prompted or set up, will automatically download and install security updates on the Windows system. Leaving room for errors, it makes sense that during a system update, there can be some glitches. Windows system update errors throw the entire move into disarray. One such constant error is the Windows Update Error Code C8000266.

When a pop up on the screen with the message: C8000266: Windows Update encountered an unknown error pops up, it signifies that the system update experienced a snag. Our technicians have compiled easy means of identifying and handling this error such that it remains just that, a snag along the way.

Windows Update Error Code C8000266 Fix

We have two main methods of getting rid of the C8000266: Windows Update encountered an unknown error pop-up notification. You can either reset all the Windows updates sections or simply run the Windows Update troubleshooter.

Ways to Fix Windows Update Error Code C8000266

We will set this article as a guideline with two fixes:

Fix #1: Reset All the Windows Updates Sections

Try manually resetting your Windows Updates Sections. To get that done, follow these commands:

1. Simultaneously press Win+R on your keyboard to launch the Run dialog box
2. In the box that opens, type in cmd then press Ctrl+Shift+Enter. This opens an elevated Command Prompt
3. An elevated Command Prompt window should appear. Into the command line, type the following successive commands followed by hitting Enter after each:
   net stop bits
   net stop wuauserv
   net stop appidsvc
   net stop cryptsvc
4. The Windows Update Service, Background Intelligent Transfer Service (BITS), and Cryptographic service will stop running.
5. Remove all qmgr*.dat files from your system to reset all Windows Update Sections. Do this by entering this command:
   Del “%ALLUSERSPROFILE%\ApplicationData\Microsoft\Network\Downloader\qmgr*.dat”
6. Type Y from the keyboard to confirm.
7. The next step is to rename the catroot2 and Software Distribution folders. Type the commands in the appropriate command prompt window and press Enter after every command:
   Ren %systemroot%\SoftwareDistribution SoftwareDistribution.bak
   Ren %systemroot%\system32\catroot2 catroot2.bak
8. Reset the Windows Update service and BITS service to their default security settings. After each command, hit Enter to execute. Type the commands below into the appropriate prompt window:
   sc.exe sdset bits D:(A;;CCLCSWRPWPDTLOCRRC;;;SY)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BA)(A;;CCLCSWLOCRRC;;;AU)(A;;CCLCSWRPWPDTLOCRRC;;;PU)
   sc.exe sdset wuauserv D:(A;;CCLCSWRPWPDTLOCRRC;;;SY)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BA)(A;;CCLCSWLOCRRC;;;AU)(A;;CCLCSWRPWPDTLOCRRC;;;PU)
9. To remove the System32 directory, type the command below in the next line followed by Enter:
   cd /d %windir%\system32
10. Redo the Registry that is associated with the Windows Update, including the related DLL and BITS files. To do so, carefully input the following long list of commands. Don’t forget to hit Enter after every command to activate them:
    regsvr32.exe atl.dll
    regsvr32.exe urlmon.dll
    regsvr32.exe mshtml.dll
    regsvr32.exe shdocvw.dll
    regsvr32.exe browseui.dll
    regsvr32.exe jscript.dll
    regsvr32.exe vbscript.dll
    regsvr32.exe scrrun.dll
    regsvr32.exe msxml.dll
    regsvr32.exe msxml3.dll
    regsvr32.exe msxml6.dll
    regsvr32.exe actxprxy.dll
    regsvr32.exe softpub.dll
    regsvr32.exe wintrust.dll
    regsvr32.exe dssenh.dll
    regsvr32.exe rsaenh.dll
    regsvr32.exe gpkcsp.dll
    regsvr32.exe sccbase.dll
    regsvr32.exe slbcsp.dll
    regsvr32.exe cryptdlg.dll
    regsvr32.exe oleaut32.dll
    regsvr32.exe ole32.dll
    regsvr32.exe shell32.dll
    regsvr32.exe initpki.dll
    regsvr32.exe wuapi.dll
    regsvr32.exe wuaueng.dll
    regsvr32.exe wuaueng1.dll
    regsvr32.exe wucltui.dll
    regsvr32.exe wups.dll
    regsvr32.exe wups2.dll
    regsvr32.exe wuweb.dll
    regsvr32.exe qmgr.dll
    regsvr32.exe qmgrprxy.dll
    regsvr32.exe wucltux.dll
    regsvr32.exe muweb.dll
    regsvr32.exe wuwebv.dll
11. The next step involves resetting network configurations that are possibly the causative agents of the error. There are only two commands to be typed. Make sure to hit the Enter button after each one of them:
    netsh winsock reset
    netsh winsock reset proxy
12. After following through, you can then restart the services that were paused in step 4. Enter the commands below to get the services running once again:
    net start bits
    net start wuauserv
    net start appidsvc
    net start cryptsvc
13. Close the Commands Prompt window by typing Exit. Hit Enter.
14. Restart your Windows PC for all the changes made above to take effect.

This is a long, manual way of solving the Windows Update Error Code C8000266. If you think that it might end up confusing you, then skip it and try out the steps outlined in fix number 2.

Fix #2: Run the Windows Update Troubleshooter

The answer to what causes the Windows Update error code C8000266 has been identified as several mistakes during the download and install process. If this is to ever happen and you don’t want to get confused, try running the Windows Update Troubleshooter.

There are two ways of running the Troubleshooter. The first involves using Microsoft’s online Troubleshooter. Microsoft’s online troubleshooter will help you fix the C800026 error and other common ones. To get started:

1. Visit the Microsoft official website to run the online troubleshooter.
2. Select your version of OS from the list. Your options include Windows 7, Windows 8.1, and Windows 10/11.
3. Accept or click Yes when prompted to run the Windows Update Troubleshooter.
4. A list of recommendations and the steps to take next will come up. Carry through and work as advised by the Troubleshooter.

The second option, which you can easily control, is to troubleshoot offline using your PC Troubleshooter.

Here’s how to run the Troubleshooter manually:

1. Launch Troubleshooter by pressing Win+I on the keyboard.
2. Navigate to Update & Security > Troubleshoot > Additional Troubleshooters.
3. On the page that opens, select Windows Update, and then hit the Run the Troubleshooter button.
4. The Troubleshooter will automatically launch and pick up any issues, then start working on resolving them.
5. Wait for the Troubleshooter to finish working, then restart your Windows PC.

Once the system has restarted, go back to doing your work. The Windows Update Error Code C8000266 should be gone by now.