The challenge you're experiencing with updating the Windows Defender definition might be due to a damaged Windows system files. It would be great if you can tell me more about your concern. Kindly answer the following questions:
When did the issue start?
Did you notice any system setting changes prior to the issue?
Are you getting any error messages?
What is the current OS Build of your Windows 10 system? You can find this information by clicking the
Start button, type
About your PC, press Enter, and then scroll down to
Definition updates for Windows Defender are automatically installed when you run
Windows Update. If your system is having trouble with installing the latest updates for Windows
10, I suggest running the Windows Update Troubleshooter. This tool will scan
and fix your device for any update issues found.
If the troubleshooter wasn't able to rectify the issue, you can manually download and install the definitions from this
page. Please follow the steps under the section: Manually download and install the definitions.
Should the issue continue, you can scan your device for corruptions in Windows system files using the
DISM command-line tool and the SFC tool. You will need administrator access to perform this operation. You can find the steps on how to run the tools from this
Are you referring to updating Windows 10 or Windows Defender? Can you tell me if you're getting an error message when updating? Can you tell me the troubleshooting steps that you've tried so far? For now, you can follow the troubleshooting steps we provided
in our previous post.
Should the issue continue, I recommend performing a clean
boot to eliminate the possibility of a software conflict. A
cleanboot is performed to start Windows by using a minimal set of drivers and startup programs. This helps eliminate software conflicts that occur when you update your system. Kindly follow the steps from this
support article on how to perform a
NOTE: Please go to the section:
Reset the computer to start normally after clean boot troubleshooting to boot the PC in normal startup after fixing the issue.