If the issue is with your computer or a laptop/notebook you should try using the Reimage Plus Software which can scan the repositories and replace corrupt and missing files.

If the issue is with your computer or a laptop/notebook you should try using the Reimage Plus Software which can scan the repositories and replace corrupt and missing files.

Once the updates are downloaded, they will be installed – successfully, this time.

Type exe -signatureupdate into the Command Prompt and press the Enter key.

This will initiate a Windows Defender update which, hopefully, will be successful.

Most users posting in that thread only see WU hang at "Checking for updates..." when it detects a large number of available updates so it's difficult to determine if any changes you've made to your system actually solve the problem until you run your next Patch Tuesday update. checking for updates was close to immediate and 20 updates were indicated ... The only thing that made me nervous was that the first part of the installation (before restart) of the Malicious Software Removal Tool was on the long side ... but that sometimes happens in the update process so I figure it's normal. Check for Updates took maybe 7 hours and still was not finished.

Ken B Some of us have been through the experience of check for updates never finishing. The next day, a notification soon cameup in task tray that Updates were avaialbe; so downloading of the updates took more than about 3 or 4 hours. I didn't install any new updates in last days except Windows Defender definitions. After installing KB3145739, it was always finished in 5-10 minutes. (WU is set to This time it was the security patch KB3153199. id=52217 (Stop WU service, install the update, restart.I uninstalled all updates and restarted the system. So I had to use my restore point to solve this problem. Many Windows 10 users have complained of Windows Defender – the Operating System’s resident antivirus programs – not updating regardless of whether the update being downloaded and installed is a small Definitions update or a large, chunky update. This works in most cases, where the issue is originated due to a system corruption.After installing KB3153199 two days ago, today I dared to install some security updates. High CPU usage came back, causing by Trusted Installer this time. You can also try updating Windows Defender using an elevated Command Prompt.