How to fix error 0xC1900101 - 0x20017 SAFE_OS phase error
Jul 26, 2025 am 01:22 AMWhen encountering Windows update error 0xC1900101 - 0x20017, 1. Unplug all non-essential peripherals, only retain the keyboard and mouse; 2. Check the hard disk status and run chkdsk, replug and unplug the memory module; 3. Completely uninstall third-party antivirus software and use the official uninstall tool; 4. Run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth with administrator permissions to repair system files; 5. If it still cannot be resolved, download the latest image from Microsoft's official website and upgrade and install it through a bootable USB disk. Following the above steps to check in turn, the update error can usually be effectively resolved.
Windows Update Error 0xC1900101 - 0x20017 Appears in the "SAFE_OS" phase, which usually means that the system has encountered problems when trying to enter safe mode for updates. This may be caused by hardware drivers, third-party software conflicts, or system files corruption. Don’t panic when encountering this error. Below are some common solutions that can be checked and fixed step by step.

Check hardware connections and peripherals
This error is sometimes caused by incompatibility of certain external devices or hardware. Especially USB devices such as USB drives, printers, and cameras may interfere with the system entering safe mode.
- Unplug all non-essential peripherals : only keep the keyboard and mouse (if it is a wired device), and unplug other speakers, printers, USB flash drives, mobile phone charging cables, etc.
- Check the hard disk status : If you are using a mechanical hard disk, it is recommended to run a disk detection tool (such as chkdsk) to scan for bad channels.
- Loose memory sticks can also cause this problem : If you are familiar with hardware operations, you can try replugging and unplugging the memory stick.
Sometimes it is just that a certain device driver is incompatible with the new version of the system, and temporarily removing it first can reduce interference.

Disable or uninstall third-party antivirus software
Many users have reported that before installing Windows updates, third-party antivirus software (such as Kaspersky, Bitdefender, Avast, etc.) will cause the system to fail to enter the SAFE_OS stage normally.
- Completely uninstall antivirus software : not just turn off real-time protection, but completely delete the program.
- Use official uninstallation tools : Some antivirus software provides special uninstallation tools (such as Revo Uninstaller or the tools provided by the manufacturer's official website).
- After restarting, try to update the installation again .
Such software often deeply integrates the system, and even if temporarily disabled, it may retain service and affect the startup process.

Use built-in tools to repair system files
If the hardware and peripherals are fine, it is likely that the system files are damaged or lost. At this time, you can use the system's own repair tools to deal with them.
- Open a command prompt (administrator permissions), and then enter the following commands:
sfc /scannow
DISM /Online /Cleanup-Image /RestoreHealth
- If the above command fails, you can try to mount the image from another Windows device that is running normally for repair.
These two tools are responsible for scanning and replacing corrupt system files, and repairing the Windows image itself. After running, try to update the installation, there is a high chance of solving the problem.
Try manually downloading the latest image upgrade
If the above methods do not work, or you don’t want to make trouble repeatedly, you can directly download the latest Windows official image for upgrade and install.
- Visit Microsoft's official website to download the Media Creation Tool or Windows 11 download page .
- Create a bootable USB drive and select the "Upgrade this computer" option to install it.
- Your files and applications will be retained during the upgrade process, but it is recommended to back up important data in advance.
This method is equivalent to skipping the automatic update mechanism and directly using the complete installation package for upgrade, which can bypass some temporary errors.
Basically these are the methods. Although this error seems scary, in most cases it is not a system crash, but a conflict between certain components. Check it in order, it can usually be done.
The above is the detailed content of How to fix error 0xC1900101 - 0x20017 SAFE_OS phase error. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

Microsoft Edge can be uninstalled, but because it is a Windows system component, it cannot be uninstalled directly through the control panel like ordinary software. 1. Use a command prompt (administrator permissions) to uninstall the Edge installation package; 2. You can disable or replace Edge with the help of third-party tools; 3. Enterprise users can manage through Group Policy. Even if uninstalled, it may still be redeployed when the system is updated. Alternatives include: setting other browsers as default, manually removing the Edge icon, and hiding Edge using scripts. Users suitable for uninstallation include system geeks, enterprise unified management needs, and low-end device users who want to release resources. Ordinary users only need to change the default browser to avoid interference.

If you want to remotely turn off the router Wi-Fi, you must first confirm whether the router supports remote management; if it does not support it, it can be achieved through a smart socket power outage; advanced users can also consider flashing in custom firmware. The specific steps are as follows: 1. Check whether the router has remote management functions, such as the manufacturer's supporting app or cloud management functions; 2. If it is not supported, purchase and set up a smart socket and remotely cut off power through its app; 3. For technical users, you can install firmware such as DD-WRT or OpenWRT to obtain remote control permissions. Different methods have their own advantages and disadvantages. Please weigh them according to your own needs when choosing.

System restore point setting methods include manual creation, dependency automatic creation, and management of storage space. 1. Manual creation requires system protection to enable in "Create Restore Point", allocate 5% disk space and click "Create" to name the restore point; 2. The system will automatically create restore points when installing updates or changing settings, but do not guarantee comprehensiveness; 3. The restore point occupies no more than 5% of the system disk space by default, and the old version will be automatically cleaned, and storage can be managed by adjusting the upper limit.

A firewall is a network security system that monitors and controls network traffic through predefined rules to protect computers or networks from unauthorized access. Its core functions include: 1. Check the source, destination address, port and protocol of the data packet; 2. Determine whether to allow connections based on trust; 3. Block suspicious or malicious behavior; 4. Support different types such as packet filtering firewalls, status detection firewalls, application layer firewalls and next-generation firewalls; 5. Users can enable built-in firewalls through operating system settings, such as Windows Security Center or macOS system preferences; 6. The firewall should be used in combination with other security measures such as strong passwords and update software to enhance protection.

When encountering the blue screen error VIDEO_TDR_FAILURE(nvlddmkm.sys), priority should be given to troubleshooting graphics card driver or hardware problems. 1. Update or rollback the graphics card driver: automatically search and update through the device manager, manually install or roll back to the old stable driver using NVIDIA official website tools; 2. Adjust the TDR mechanism: Modify the TdrDelay value in the registry to extend the system waiting time; 3. Check the graphics card hardware status: monitor the temperature, power supply, interface connection and memory module; 4. Check system interference factors: run sfc/scannow to repair system files, uninstall conflicting software, and try safe mode startup to confirm the root cause of the problem. In most cases, the driver problem is first handled. If it occurs repeatedly, it needs to be further deepened.

To prevent specific programs from being connected to the network can be achieved through system firewalls or third-party tools. 1. Windows users can use their own firewall, create new rules in the "outbound rules" to select the program path and set "block connection"; 2. Third-party tools such as GlassWire or NetBalancer provide graphical interfaces that are more convenient to operate, but pay attention to source reliability and performance impact; 3. Mac users can control networking permissions through the command line with pfctl or using LittleSnitch and other tools; 4. A more thorough way is to use the network outage policy. The whitelisting policy prohibits all programs from being connected to the network by default and only allows trusted programs to access. Although the operation modes of different systems are different, the core logic is consistent, and attention should be paid to the details of the path and scope of the rules taking effect.

First, confirm the high CPU occupancy process, open the task manager to view the "CPU" tab; secondly, search the process name to determine whether it is a system or a third-party program; try to end non-critical processes, close unnecessary browser tags or plug-ins; update drivers and system patches; close unnecessary startup items; use professional tools to further analyze. The above steps can usually effectively solve the problem of computer lag.

UAC frequently pops up because the running program requires administrator permissions or the system setting level is too high. Common reasons include installation of software, modifying system settings, running third-party tools and other operation triggers. If using an administrator account, UAC only confirms the operation and not blocks. The methods for reducing prompts include: canceling the program to run as an administrator, lowering the UAC notification level, using a standard user account, and starting the program through the task planner. It is not recommended to turn off UAC completely because it can effectively prevent malicious programs from tampering with the system. You can set the UAC to "notify only when the program changes the computer" to balance security and experience.