A lot of errors could appear when you are running Windows. The unknown hard error is a common one that many users said they have met. It often turns the screen black and stops users from doing anything. How terrible it is! I would like to offer useful ways to help Windows users fix the unknown hard error and rescue data from the computer which cannot log in.

Seeing an error message when you are working on a Windows computer is an unpleasant experience. Recently, people complained they have met unknown hard error in 1803 (and other versions). In fact, this hard error message could appear on any Windows systems in many cases.

unknown hard error

Now, I’m going to analyze it for you.

Unknown Hard Error on Windows 10 after Update

The unknown hard error may show up on your screen when you are doing the following things:

  • Updating Windows systems
  • Playing a game online
  • Using various programs at the same time
  • Opening or closing applications
  • Executing commands or files

Statistics show that the automatic Windows update is the most common reason that causing the problem.

Tip: Sometimes, the update succeeds, but it has deleted some files that are useful to you from the computer. You should start to recover files after Windows Update without any delay in such case.

Specific Case of Unknown Hard Error after Update

Windows updated last night, can’t work today.

Hi. So, my lenovo Z51 was working perfectly, however last night Windows updated and today. It’s not working. When I turn on the laptop the first error pops up just before I type in my login details. Ctfmon.exe – success Unknown hard error. I then click OK and it says Sihost.exe – system warning Unknown hard error. I then click OK and I can type my username and password and it takes a long time to log in. The most recent try it just continues spinning the welcome message and doesn’t log in properly. My desktop now has no icons, except the recycle bin (which it doesn’t let me view) and I can’t go in explorer to see my docs etc. (it takes a very long time to log in, and doesn’t work every time) The WiFi isn’t working, although device manager says it is enabled. I have started in safe mode via msconfig, also disabled all of the startup programs but no change. Explorer.exe isn’t running in task manager so I can’t exit it and restart it. I can’t get into control panel either and do a system restore. If I click on the start button or right click on the taskbar, nothing happens. I am not hugely techy but I am competent in Windows and have been fiddling around today and can’t get it resolved. It’s very frustrating that the windows update has done 🙁 Any help would be greatly appreciated as I use the laptop for work.– said Windowzupdate on BleepingComputer Support Forum

Obviously, Windowzupdate is troubled by the Windows unknown hard error. Let me summarize the problem for you:

  1. He tried logging into the system but failed.
  2. He saw the Ctfmon.exe and Sihost.exe Unknown hard error.
  3. After clicking on OK, he typed the username and password (the welcome message is spinning and login failed).
  4. He found only Recycle Bin icon on the desktop, but he couldn’t view it. He also failed to access files via Windows Explorer.
  5. The WiFi is not working even though the Device Manager said it was enabled.
  6. Starting in safe mode and disabling startup programs didn’t work.
  7. exe wasn’t running in Task Manager so it can’t be ended.
  8. Access to Control Panel and System Restore failed.
  9. Start button and taskbar was not responding.

Fix Unknown Hard Error on Windows 10

How terrible the situation is if you are totally at a loss when seeing the unknown hard error! Want to get rid of the annoying unknown hard error? I think you should complete the following two things:

  • Recover data from that hard disk quickly.
  • Try the solutions that will be mentioned later to fix the error.

Step One: Ensure Data Security

  • The unknown hard disk error will prevent you from accessing data.
  • The fixes to solve the problem may bring data loss sometimes.

As a result, I think it’s necessary to get data off the disk with errors. Please follow this tutorial to get data back with ease.

Stage 1: create a bootable disk.

Certainly, your operations are limited when you are working on a computer with an unknown hard error. Therefore, I think you should use a bootable disk to access your hard disk data without booting system.

  1. Find another computer that works well and get a suitable version of MiniTool Power Data Recovery. In order to create a bootable disk to recover data from hard disk without OS, you should choose a license that contains a Snap-in WinPE Bootable Builder (I advise the Personal Deluxe license if you don’t have special needs).
  2. Install the software and run it. Then, copy & paste the license code to register (I’ll take the Personal Deluxe version as an example).
  3. Click on the Bootable Media button in the lower left corner to start MiniTool Media Builder.
  4. Click on the WinPE-based media with MiniTool plug-in option.
  5. Choose media destination from ISO file, USB Flash Disk, and CD/DVD Writer. (If you forget to connect the USB flash drive or CD/DVD disk to the computer in advance, please connect it now and click on the Refresh button.)
  6. Choose Yes in the pop-up window to confirm.
  7. Wait for the Building a bootable USB disk (or Building a bootable CD/DVD) to complete.
  8. Click on the Finish button and eject the USB disk or take out the CD/DVD from the computer properly.

Do You Really Need To Safely Remove USB Device?

license comparison

click Bootable Media

building finished

Stage 2: boot computer with the bootable disk.

  1. You should remove the bootable USB flash drive (or CD/DVD) from the current computer.
  2. Then, connect it to the computer that has Unknown Hard Error.
  3. Restart the computer and enter BIOS settings by pressing a certain button.
  4. Move the USB disk/CD/DVD to be the first device under Boot tab of the Setup Utility.
  5. Choose Exit and press Yes to save the configuration changes.
  6. Click on the OK button in the screen resolution changing window and software launching window.
  7. Select the first option – MiniTool Power Data Recovery – in the MiniTool PE Loader window.

exit and save changes

launch MiniTool Power Data Recovery

Stage 3: recover data from hard disk.

  1. Connect a removable disk to the computer (it should have enough free space to store the needed files on hard disk).
  2. Shift to the Hard Disk Drive option from This PC option (which is selected by default).
  3. Confirm the disk that contains files you need.
  4. Double click on the disk or click on the Scan button to start searching for files.
  5. More and more files will be found by the software; you can browse them to see whether your needed files are included or not.
  6. If you can find the files you want to recover, please select them and click on the Save If not all files you need are here, please wait for the scan to complete and then select files & click on the Save button.
  7. Choose a safe place as the directory to store the files that will be recovered.
  8. Click on the OK button and wait for the recovery process to complete.
  9. Choose Yes in the success window that appears when all selected files have been recovered.


save files

The above 3 stages tell exactly how to create a removable boot disk, how to boot the computer without OS, and how to recover data from the corrupted internal hard disk. They also work when you see Operating System Not Found/Missing Error and can’t enter the OS.

Click to Tweet

To prevent further damage, you should hurry to troubleshoot the unknown hard error on Windows 10 after update by following ways.

The first way: perform a clean boot.

Attention: you need to log in Windows 10 as an Administrator before you do the following things.

  1. Click on the Start button in the lower left corner.
  2. Scroll down to find Windows System folder and expand it.
  3. Select Run to open the dialogue box.
  4. Type msconfig and press Enter on the keyboard.
  5. Shift to the Selective startup option from Normal startup under Startup selection in the General tab.
  6. Uncheck the Load startup items option.
  7. Shift to the Services tab.
  8. Check the Hide all Microsoft services option at the bottom.
  9. Click on the Disable all button.
  10. Click on the OK button to close System Configuration.

clean boot

This method is able to solve the unknown hard error caused by software conflict or problematic software.

The second way: use System File Checker tool.

  1. Right click on the Start button in the lower left corner.
  2. Choose Windows PowerShell (Admin) from the pop-up menu.
  3. Type sfc /scannow into the window and press Enter on the keyboard.
  4. You’ll see prompt: Beginning system scan. This process will take some time. Just Wait for the scan to complete.

System File Checker

This is the most primitive method, but its capability is very strong; it’s able to fix a lot of problems related to the internal system.

The third way: uninstall recent software and updates.

  1. Press Win + I buttons on the keyboard to open the Settings window.
  2. Scroll down to select Update & Security (Windows Update, recovery, backup).
  3. Windows Update will be checked by default. You need to click on View installed update history option from the right panel.
  4. Then, click on the Uninstall updates option in the View installed update history window.
  5. Pick out the update that you have installed recently and may be responsible for the error.
  6. Click on the Uninstall button and choose Yes in the User Account Control window to allow change.
  7. Repeat step 5 ~ step 6 to uninstall all recently installed software and updates.

uninstall update

This method is useful when the error is caused after the installation of the automatic updates.

Note: If you can’t boot into your system after updating the BIOS, you must be worried, right? This post is going to help you solve the PC not booting problem and rescue your precious data in easy steps.

If the system doesn’t allow you to uninstall the update via Windows Settings, you’ll need to rely on System Restore.

  1. Tap the Cortana icon on the taskbar.
  2. Type create a restore point into the search box.
  3. Choose Create a restore point (Control panel) from Best match.
  4. Click on the System Restore button under System Protection tab.
  5. Click on the Next button in the System Restore window.
  6. Figure out which restore point was created before the Windows 10 Unknown Hard Error.
  7. Select the proper restore point and click on the Next and Finish buttons.
  8. Restart the computer.

System Restore

That’s all about what you should do to deal with the unknown hard error on Windows 10.

Click to Tweet

Cause and Effects of the Unknown Hard Error

5 Possible Causes

A lot of reasons could lead to the Unknown Hard Error, for instance:

  • The disk is damaged.
  • The device drivers are incorrect.
  • The system is attacked by a virus or malware.
  • The system files are is corrupted or configured incorrectly.
  • There is an error in the Windows Registry due to recent software change.
Tip: The virus/malware invasion may also cause data loss, apart from system errors. So I guess you may want to know how to recover files lost by virus attack.

You will see the following error messages when encountering unknown hard error Windows 10 login.

  • Ctfmon.exe – Success: Unknown Hard Error
  • Sihost.exe – System error/System Warning: Unknown Hard Error
  • Explorer.exe – System Warning: Unknown Hard Error

error messages

6 Common Effects

The unknown hard error is not restricted to real Windows 10 computer; it is also possible to appear on VMware (click here if you need to recover data from VMware disk). You will be kicked out of the system when seeing the unknown hard error on Windows. Besides, the unknown hard error will also cause the following troubles:

  • Windows 10 black screen
  • Windows 10 taskbar not working
  • Icons disappearing from Windows 10 desktop
  • WiFi not working
  • 100% disk usage
  • Slow boot and slow responding
  • Etc.

Last Words

On Windows 10, ctfmon.exe unknown hard error, sihost.exe unknown hard error, and explorer.exe unknown hard error could appear now and then. Ordinary users often don’t know how to deal when stuck in such a dilemma.

Therefore, I feel it’s necessary to help you rescue data from the problematic disk and teach you some practical ways to fix the error. Besides, I have listed the possible reasons for causing an unknown hard error and the consequences it will bring; in this way, you can do your best to prevent the error.

If you still can’t settle the problem down, please feel free to contact MiniTool support team.

Unknown Hard Error FAQ

? What is a hard error?
Hard errors occur now and then on your computer, just like the chip-level soft errors. A hard error is usually caused due to issue in RAM. The root reason is the permanent physical flaw in the module which can be resulted from the hardware failure or defect.
? What does it mean when my laptop says unknown hard error?
When you see the unknown hard error on your laptop, it means a physical flaw is found by system and this can’t be fixed if you rebooted the computer. In fact, the unknown hard error will show up when your internal hard drive is corrupted.
? How do you fix Windows 10 when it fails to boot?
  1. Check the battery if it is running on a laptop.
  2. Remove all the USB and external devices.
  3. Try to disable the fast boot.
  4. Try to boot into Windows Safe Mode.
  5. Boot to the Command Prompt.
  6. Scan your computer for virus.
  7. Try System Restore.
  8. Perform a Startup Repair.
? What does SIHost.exe mean?
To be specific, the SIHost stands for Shell Infrastructure Host which is a core component of Windows operating system. Meanwhile, the .exe is a common suffix that refers to an executable file. The Sihost.exe is able to run the Shell Infrastructure Host.
  • linkedin
  • reddit