Windows defender error 0x800700AA, service can not be started comes when the user is trying to run Windows defender scan on their system.
This kind of behavior happens for two reasons mostly, third-party application conflict or corrupted system files.
In this article, we will tackle both scenarios and provide you with solutions in both cases.
In this rare scenario when Windows defender can not start scan due to conflict with installed service or application in the system solution is quite simple. Restart your PC into safe mode and run the scan from there. In a safe mode environment, minimum drivers and services are only loaded eliminating any conflicts that might occur when everything is booted. If Windows defender can not run the scan in safe mode and you get the same 0x800700AA error then you can eliminate application conflict as a reason and move to the next solution which will tackle corrupted system files. If you, however, managed to run a scan then you have a rare third-party application conflict, you can boot normally into windows and try to eliminate one by one to see which one is causing the issue. The safest bet would be to start with security software because most of the time that is what causes conflicts in running services and applications.
If the previous solution has not provided you with results then you have system file corruption that needs to be fixed. Move from one solution to another as presented below:
SFC scan is a built-in Windows tool for solving corrupted system files issues, it is fully automated and does not require from the user any kind of knowledge or information. To run it and scan the system do the following:
Press ⊞ WINDOWS + X to open the secret menu
Left-click on the command prompt (admin)
In command prompt type SFC /SCANNOW and press ENTER
Wait for the process to finish, do not interrupt it and once it is done, restart your computer
DISM scan is similar to SFC scan but it tackles different types of system file corruption and it is recommended to run it also after SFC has been completed. Please note that for DISM scan to be successful you will need a stable internet connection since DISM will replace corrupted files with new ones downloaded from Microsoft. To run it do the following:
Press ⊞ WINDOWS + X to open the secret menu
Left-click on the command prompt (admin)
inside command prompt type: exe /online /cleanup-image /scanhealth followed by ENTER, then type: Dism.exe /online /cleanup-image /restorehealth also followed with ENTER.
Leave scan to finish and reboot your PC

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Tracked as CVE-2021-34484, the “zero-day” flaw enables hackers to breach all versions of Windows (including Windows 10, Windows 11, and Windows Server 2022) and take control of your computer.
Microsoft mistakenly thought it had patched the vulnerability (which was first found in August) when it was publicly disclosed in October. But the fix itself was found to be flawed, something the company admitted, and this drew even more attention to the vulnerability. Microsoft subsequently promised to “take appropriate action to keep customers protected” but two weeks later, a new fix has still not arrived.
Luckily the third-party security specialist 0patch has beaten Microsoft to the punch with a ‘micropatch that it has now made available for all Windows users “Micropatches for this vulnerability will be free until Microsoft has issued an official fix," 0patch confirmed.
You will need to register for a 0patch account and install its download agent before the fix can be applied, but with 0patch fast becoming a go-to destination for hot fixes which beat software companies to the punch this is a no brainer. Hopes will be high that Microsoft can release an effective patch sooner rather than later but, until then, all Windows users must act now if they want to be safe.
Download 0patch here:
https://blog.0patch.com/2021/11/micropatching-incompletely-patched.html MySearchDial is a browser hijacker that typically comes bundled with free software on the internet. This web platform designed for searching the internet and offers the installation of its software. This software injects itself into browsers and gains access to your settings, browsing data & user information. This data is distributed to the ad providers without limitation. While covered by their EULA, most users will be unaware of what they agree to with checkboxes selected by default. The software also adds a huge amount of registry keys and links throughout the operating system. Since the software injects itself into many personal files, removing the software results in a total reset of your browser settings. For these reasons MySearchDial is classified as potentially unwanted and is flagged for removal by a number of internet security utilities.
Option to right-click on the taskbar and launch task manager is gone but do not worry there are other same and simple ways you can launch it.
Web Shield is a free application that allows you to view insightful analyses about the websites that you visit and specifically how they’re tracking you online. Web Shield cannot determine exactly who is tracking your computer usage. Instead, Web Shield allows a user to see which websites have placed tracking code onto their computer.
This software is ad-supported and displays advertisements in the form of injected banner ads, popups, and context hyperlinks in the user’s web browser. It adds Windows Background services, displays unwanted advertisements, and can modify the browser’s home page.
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