Repair or reinstall Windows Update
The "joys" of Windows Update not working in Windows XP, Vista, 7, 8 and 8.1 are numerous. This might end with not receiving or not being able to install updates, repeated installation of same updates, or in worse cases, endless reboot cycles in Windows Vista, 7 or 8/8.1.
First, check if you have enough free disk space (at least 1 gigabyte) on your hard drive. If not, read the Remove temporary files article on how to get rid of unnecessary files with CCleaner.
Second, verify that time and date are correct on your PC - a date in the past or the future prevents both Windows Update and Genuine Windows Validation tool from working properly.
Third, have you tried restarting your computer? The simple move might fix problems with locked files and make everything right again.
Luckily there are options for quickly fixing Windows Update problems or completely reinstalling it in Windows XP, Vista, 7, 8 and 8.1.
You can also run the tools listed below in Safe Mode with Networking, although they might then tell you that problems were not fixed.
Common Windows Update problems
In case your PC crashes with error code 0xc000021a (and displays error "Your PC couldn't start properly" with code 0xc0000001 after several reboots) right after installing latest updates, you need to run disk check to fix file system corruption. Instructions are available for Windows XP, Windows Vista and 7, Windows 8 and 8.1.
If the same error appears even after file system repairs, you must boot into Command Prompt of Windows RE (just like in the fixing disk errors tutorial linked above) and run DISM to revert pending actions. This command is available only in Windows 7 and later.
In Command Prompt, type dism.exe /image:D:\ /cleanup-image /revertpendingactions and press Enter to run the command. Replace D:\ with the correct letter of the drive where Windows is installed (use bcdedit | find /i "OSDEVICE" command to determine the drive letter). Ignore error messages about scratch directory size.
Close Command Prompt window and reboot your PC. Windows should start normally now.
Windows XP users must have Service Pack 3 installed to use Windows Update or Microsoft Update. Without it, "Error number: 0x80190194" failure message appears while searching for updates.
If you experience serious and prolonged (several hours) slowdowns in Windows XP while Windows Update is searching for updates, and Task Manager shows that svchost.exe is constantly using 99-100% of CPU resources, see this tutorial at www.winhelp.info. This applies to brand new (aka clean) installs of Windows XP Service Pack 3, and to those who have long turned off automatic updates and now want to apply latest patches.
In case applying .NET Framework patches ends with errors 66A or 8007066A, you need to run Microsoft Fix It Tool 50123 that repairs MSI software update registration corruption issues.
If you experience trouble with Windows Store (updating apps, browsing the Store, etc), open Start screen, type wsreset, right-click the result and choose Run as administrator.
As usual, User Account Control pops up, click OK. After a while, Windows Store cache is cleared and you can probably use the app normally.
But if you are still facing issues with Modern UI/Windows Store/Metro apps, please see how to fix Photos, PC Settings, or all apps.
Windows 8/ 8.1 users can open Settings search using keyboard shortcut Windows Key+W (or by swiping in from the right edge of screen and tapping Search icon). Type troubleshoot and click or tap Troubleshooting.
Then click Fix problems with Windows Update in the System and Security section.
Click Advanced, verify that Apply repairs automatically is enabled and click the Run as administrator link.
You might have to restart your computer for changes to take effect.
If this does not resolve the problems, see System Update Readiness Tool.
Automated troubleshooter works in all supported Windows versions (from XP to 8.1).
First thing to try is to open Microsoft's How do I reset Windows Update components page.
If the following dialog pops up on the web page, click Run now.
If the pop-up does not appear, expand the appropriate section (Windows 8 and Windows 7, also applies to Windows 8.1; or Windows Vista and Windows XP) and click the run now button.
Click Detect problems and apply the fixes for me (Recommended).
The Fix It tool will then create a System Restore Point, download Windows Update components and run fixes. This usually takes a few minutes only. Click Next after the process is complete.
Please note that in Safe Mode the Fix status column will always state "Not fixed" because Automatic Updates service cannot be started.
After this, you can test if Windows Update works correctly. Closing the Fix It tool is optional.
If you want to give feedback to Microsoft, choose an option in Did this fix your problem screen and click Next.
Finally, click Close in the Thank you screen.
Fix It 50202 works in Windows XP, Vista and 7 only.
If the first option did not help, Microsoft also has the very powerful Fix It Tool 50202 that completely reinstalls Windows Update components. This one is especially helpful in cases where Windows Update is not able to check for updates (for example, error 800700C1) or installs the same updates all over again (several cases with infinite loops of .NET Framework updates).
Because Microsoft just loves to move the tool randomly around (and its site search is not helpful either), I now provide direct download link to Fix It Tool 50202.
Please save the file, do not run it automatically!
After downloading is complete, run the program (named MicrosoftFixit50202.msi).
Click I Agree in the License Terms page and then click Next.
As you can see, the Run aggressive options (not recommended) check box on Additional options screen is unchecked. I strongly suggest to execute the repairs without enabling aggressive options for the first time - this will retain all Windows Update and Microsoft Update settings.
In Windows Vista and 7, User Account Control will appear. Click Continue or Yes.
The tool will then create a System Restore point and run the fixes. Some files might be downloaded during the process.
After the program has done its job, click Close.
A prompt to restart your computer appears. Save open documents and close all open programs. Then click Yes.
Verify that Automatic Updates, Windows Update or Microsoft Update works. If not, re-run the Fix It Tool 50202, but tick the Run aggressive options (not recommended) check box this time.
After using aggressive options, you must configure Windows Update again.
Using the aggressive options also clears update history, but the list of applied updates can still be found in Control Panel.
In Windows XP, open Control Panel and click Add/Remove Programs. Then tick the Show updates check box and choose Date Last Used from the Sort by combo box. The latter sorts updates by their install date.
In Windows Vista and newer, open Control Panel and click Programs and Features (or Uninstall a program if using Category view). In Windows 8 and 8.1, you can also use keyboard shortcut Windows Key+X to reveal the Quick Links menu and click Programs and Features (the topmost item) there.
Then click View installed updates on the left.
To sort the list by date, click Installed On column once. Clicking it again reverses the sort order.
System Update Readiness Tool is available for Windows Vista and later. It can resolve problems with broken update packages and damaged system files.
Windows Update error 80246002 (Windows could not search for updates) in Windows 7 is one example where other tools fail and System Update Readiness Tool works perfectly. The trouble often starts after automatic upgrade of Windows Update Agent to version 7.6.7600.320 in August, 2014.
Go to Microsoft's What is the System Update Readiness Tool? page and download the package that applies to your computer. Please see Windows article for instructions on how to find out which version and architecture your device has.
Click Download again in Microsoft Download Center page. Please note that the file is over 200 megabytes in size for 32-bit Windows, and over 500 megabytes for 64-bit Windows.
After launching the downloaded package, click Yes to install it.
System Update Readiness Tool installation takes easily 10 minutes or more to finish, even over an hour on slower computers is possible. It does not usually require a reboot.
Click Close after the installation is complete. Windows Update should be running fine now.
Next steps if all options fail
In case neither of the recommended actions help you get Windows Update running, do not rush into formatting drives and performing clean install of Windows.
With the sad exception of Windows Vista, you can do a non-destructive reinstallation of any version of latest Windows. This will keep your personal files and settings, installed programs and apps, and return Windows to a fully working state.
The guides for different versions are listed below:
- Non-destructive reinstall of Windows XP
- Non-destructive reinstall of Windows 7
- Non-destructive reinstall of Windows 8 and 8.1