The “Unknown Hard” error that keeps on appearing in Windows 10 can put users in an unpleasant situation. This kind of error leads to the freezing of the taskbar, blackening of the screen, and sudden disappearance of the icons on the Desktop. And each time you try to open Windows, the system will only give you an error message saying that it’s a critical error and some applications like Start and Cortana won’t work.
Upon analysis, it seems that the “sihost.exe” is not responding and that it is the one that’s causing the c000021a Unknown Hard error to pop up. Sihost.exe files represent the Shell Infrastructure Host which is an essential component in the Windows operating system. The Windows Shell Infrastructure Host is primarily responsible for handling some graphical elements of the operating system interface such as the Start menu and the taskbar transparency. And so if the Shell Infrastructure or Sihost.exe has stopped, has been removed, or corrupted, you will most likely have issues with the overall functionality of the Windows operating system and you’ll get the Unknown Hard error
In addition, the ctfmom.exe Unknown Hard error may also occur due to incompatible drivers installed on your PC. Ctfmom is a process that identifies inputs such as handwriting, languages, and many more. It’s the one that controls the functions of background behavior. To resolve this issue, you need to first try to identify which application is the one that’s running the sihost.exe file. And if needed, you need to either update or reinstall or completely uninstall the problematic application.
The SFC Scan or System File Checker, us a built-in utility in Microsoft Windows that can be found in the C:\Windows\System32 folder. This tool allows users to scan and restore any corrupted system files in Windows that might be causing the Unknown Hard error to appear. Before you use this tool, make sure to find out whether the sihost.exe on your computer is a Trojan that you have to remove or if it’s a file that belongs to a trusted Windows application. Once you have that sorted out, follow the steps below.
The command will start a system scan which will take a few whiles before it finishes. Once it’s done, you could get the following results:
You can also try using System Restore. This is one of the ways you can use it to back up your PC. Since restore points are created automatically each week by System Restore, you can use System Restore to restore your computer back to an earlier good point in time.
Putting your PC in a Clean Boot state can help you diagnose and troubleshoot the issues in your system. During this state, you can start the system with a minimum number of drivers and startup programs that will surely help you in isolating the root cause of the Unknown Hard Error.
After putting your PC in a Clean Boot State, try creating a system restore point and see if the problem still occurs. Clean Boot troubleshooting is designed to help you isolate the problem. For you to execute a clean boot troubleshooting, you must do a couple of actions (the steps are given above) and then restart your PC after every action. You might have to disable one third-party app after the other to really isolate the issue. And once you’ve narrowed down the problem, you can either disable the third-party app that’s causing the problem or remove it. Note that you must switch your PC back into the Normal Startup mode after you’re done troubleshooting the problem. Here’s how you can do it:

Error Causesresource setautoreset true C:
net stop wuauserv net start cryptSvc net start bits net start msiserver
net start wuauserv net start bits
Error Causes“Updates failed. There were problems installing some updates, but we’ll try again later. 2019-07 Cumulative Update for Windows 10 Version 1903 for x86-based Systems (KB4507453) – Error 0x80073701”The Windows Update Error 0x80073701 also comes with a code “ERROR_SXS_ASSEMBLY_MISSING” which indicates that some system files are missing on your computer that caused the update installation failure error. Although this Windows Update error does not cause any severe issues, it is still being reported in the section of Windows Update where it is marked as “Update failed”. There are several potential solutions you can check out to resolve this error. You can try to run the DISM tool or the SFC or System File Checker scan. You could also try to run the Windows Update troubleshooter. For more information, make sure to follow the options given below.
DISM.exe /Online /Cleanup-Image /RestoreHealth /Source:C:RepairSourceWindows /LimitAccess
It would be very difficult to even start a free eMail list without mentioning Google's Gmail. Introduced all the way back in 2004 as an invite-only service it became over time the most popular email platform largely due to the fact Google is offering free eMail accounts.
There are a lot of good things to be said about Gmail itself, most of the area is clutter-free and the largest space is reserved for eMail itself letting users focus on what is important. WEB client itself means that you do not need to have any application installed on your device, altho via Google chrome, you can use Gmail offline offering you flexibility if needed.
The ability to connect and manage other accounts like Outlook, Yahoo, etc is just making Gmail even more attractive, and the snooze feature is a really neat little detail that will pause eMail notifications if you need to focus on other things.
Lack of organizing messages into folders is a little confusing since Gmail offers its own unique label system but sometimes I need to have old reliable save eMail to folder.
All in all, Gmail is a great service and it offers a great eMail on the go experience.
Free Windows eMail client simply called Mail is what was once outlook express. Mail itself has the ability to work with other popular accounts like Google Gmail account, Yahoo, iCloud etc. How it comes with Windows OS and it integrates very well with Microsoft Calendar, this eMail client is for many the first choice.
On the negative side, I might say this is a strip-down version of Outlook which is paid solution so some features are missing if we would compare the two.
Overall, a simple and nice eMail client worth your time, especially if you are on the Windows platform.
Great eMail client matching in functions against paid and premium solutions of big tech companies. Fueled with plenty of customization options and reskinning ones this eMail client offers a lot for its free price tag.
It is also fueled by Mozilla community focusing on privacy and security. It can work with any mail service and it is lightweight with a clean look, altho the look itself can be heavily customized.
The bad side is that client itself relies on email services to provide cloud-based emails, so if you are receiving your email via a service that does not have a cloud-based service in itself all of your received emails will be locked to the computer where you have received them. Also customizing it can be sometimes a little too technical for the average computer user.
All in all, Thunderbird is one great eMail client and it would be a shame not to use it because of its technical side, if you need a reliable and secure eMail client on a single machine, look no further than Thunderbird.
Outlook comes as a part of the Microsoft Office suite and as one of the oldest eMail clients, it is still widely popular and adopted through many users and businesses. It has tight integration with all Microsoft services and full integration with Calendar making it one of the if not the best eMail client out there.
Outlook also has a free online service completely free for personal use as well.
The downside is that you can not get it as a separate product if you want a business version other than as a part of the Office suite.
The final verdict would be that this is perhaps the best eMail client out but the big downside is that there is no desktop version outside the Office suite.
eM Client offers a wide array of features, including a calendar, contacts, and chat. Support is provided for all the major email services including Gmail, Yahoo, iCloud, and Outlook.com. The latest version also offers PGP encryption, live backup, basic image editing capabilities, and auto-replies for Gmail.
Its automatic system makes it very easy to get emails from other services since there is no manual setting, all that is needed is to type in your email and eM Client will do everything else automatically.
A one-time purchase is not pricy and it could offer some features that some free clients are missing. Go check it out with a free trial and see if it is for you.
This eMail client's main focus is the simplicity of use with visual appeal while tackling multiple eMail accounts. It has many built-in apps along with a customizable interface. Unlike some more Microsoft-centric email clients, Mailbird Business supports a diverse range of integrated apps, including WhatsApp, Google Docs, Google Calendar, Facebook, Twitter, Dropbox, and Slack, all making for a better-streamlined workflow.
The downside of this client is the yearly subscription plan. I think people, in general, want to get away from software subscription plans so I will include this as a downside but bear in mind it is downside just in terms of a business plan not in the client itself.
Inky is eMail client if you are looking for security. It uses AI along with machine learning in order to block all types of phishing attacks that can get through to other clients. The proprietary machine learning technology can literally read an email to determine if it has phishing content, and then is able to quarantine the email or deliver it with the malicious links disabled. It also takes things a step further and offers an analytics dashboard, which allows an administrator to see patterns of attacks based on dates, or targeted users.
The downside is that client itself is so much focused on security that sometimes some nonsecurity features get overlooked and provide a poor experience but if you need a good and greatly secured eMail client Inky is one to check out.