How to Fix SAFE_OS Error During Windows 11 Installation

Error 0xC1900101-0x20017 during Windows 11 installation occurs due to driver compatibility issues or conflicts when using external drives for installation, and to resolve it, you need to check hardware compatibility, update drivers, use offline installation, or perform a clean system installation.

Table of Contents

• What does error 0xC1900101-0x20017 mean
• Main causes of the error
• Step-by-step solutions to fix the error
• Considerations when using external drives
• Alternative Windows 11 installation methods
• Checking system requirements

What does error 0xC1900101-0x20017 mean

Error 0xC1900101-0x20017 is a common error message when installing or updating Windows 11, indicating a failure at the SAFE_OS (Secure and Fast OS) stage during the boot operation. This installation phase is critical as it includes installing the basic operating system components needed for subsequent booting.

As noted by experts from Tips 2 Fix, the 0xC1900101 code is often observed at various stages of the update process and is also called a general rollback code, which indicates the presence of an incompatible driver.

It’s important to understand that the error occurs specifically when trying to complete the installation after rebooting the system, when Windows attempts to boot the new operating system but cannot do so due to hardware or driver conflicts.

Main causes of the error

Based on analysis of various sources, there are several main causes that trigger error 0xC1900101-0x20017:

Incompatible drivers

The most common cause is the presence of incompatible hardware drivers that conflict with the new version of Windows 11. This especially concerns video card drivers, network adapters, and other peripheral devices.

External drive issues

As mentioned in your case, using external drives for installation can cause problems. The flash drive should be properly formatted and have sufficient read/write speed.

BIOS/UEFI settings

Incorrect BIOS settings such as:

• Enabled virtualization
• Non-standard boot parameters
• Issues with Secure Boot

Insufficient free space

Although you have 45 GB of free space, the installation may temporarily require more space for deployment files.

Software conflicts

Background programs or antivirus software may interfere with the installation process.

Step-by-step solutions to fix the error

1. Update drivers before installation

Before attempting to update, ensure all drivers are updated to the latest versions compatible with Windows 11:

1. Visit your laptop manufacturer’s website
2. Download the latest driver versions for Windows 11
3. Pay special attention to drivers for:
   • Video card
   • Network adapter
   • Storage controller
   • Chipset

As recommended by Windows Circle, updating drivers is one of the four quick solutions to fix the SAFE_OS error.

2. Using clean boot mode

Clean boot mode allows you to start Windows with a minimal set of drivers and programs:

1. Press Win + R, type msconfig and press Enter
2. Go to the “Services” tab
3. Check the “Hide all Microsoft services” box
4. Click “Disable all”
5. Go to the “Startup” tab and click “Open Task Manager”
6. Disable all startup items
7. Restart the system and try to install Windows 11

According to experts from Tips 2 Fix, in clean boot mode, the computer starts with a pre-selected minimal set of drivers and startup programs, which allows the update to be performed.

3. Check and fix disk errors

You have already performed CHKDSK check, but to completely solve the problem:

chkdsk C: /f /r

It’s also recommended to check system file integrity:

sfc /scannow
DISM /Online /Cleanup-Image /RestoreHealth

4. Reset update components

Sometimes the problem may be related to the Windows update cache:

1. Open Command Prompt as administrator
2. Execute the following commands one by one:
   cmd

   net stop wuauserv
   net stop cryptSvc
   net stop bits
   net stop msiserver
   ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
   ren C:\Windows\System32\catroot2 catroot2.old
   net start wuauserv
   net start cryptSvc
   net start bits
   net start msiserver
   

5. Change BIOS/UEFI settings

As mentioned in Auslogics, an effective workaround is to change the number of active cores in BIOS:

1. Restart the computer and enter BIOS/UEFI
2. Find the CPU settings
3. Change the number of active cores to 1
4. Save settings and exit BIOS
5. Try to install Windows 11

Also check:

• Enable Secure Boot
• Disable Fast Boot
• Make sure SATA mode is set to AHCI

Considerations when using external drives

The external drive issue described in your case is common. Here are several recommendations:

Flash drive formatting

For successful Windows 11 installation from an external drive:

1. Format the flash drive to NTFS file system (as you have) or exFAT
2. Ensure the flash drive has a read speed of at least 15 MB/s
3. Use a quality class 10 flash drive or higher

Alternative methods for working with external disk

1. Temporarily copy files to the main drive

   • Copy installation files to the main drive
   • Run installation from there
   • After successful installation, delete temporary files

2. Use a different flash drive

   • Try using a different flash drive
   • Make sure it’s not damaged

3. Disable Bluetooth and wireless devices
   As noted in Diskpart, some users report that disabling Bluetooth and wireless devices in BIOS helps fix the Windows update problem.

Alternative Windows 11 installation methods

1. Offline installation

Instead of using Windows Update or Assistant, create an offline installer:

1. Download the Windows 11 Media Creation Tool
2. Run it and select “Create installation media for another PC”
3. Create a bootable flash drive
4. Restart the computer and boot from this flash drive
5. Perform a clean Windows 11 installation

2. Update through Windows Insider Program

If you can’t wait for the official Windows 11 25H2 release:

1. Join the Windows Insider Program
2. Install the Windows 11 preview version
3. After successful installation, update to the stable version

3. Use Virtual Machine for testing

Before the main installation, you can test compatibility in a virtual machine:

1. Install VirtualBox or VMware
2. Create a virtual machine with Windows 10
3. Try to install Windows 11 in a virtual environment
4. If successful, repeat on the main computer

Checking system requirements

Ensure your computer fully meets Windows 11 requirements:

1. Processor: 1 GHz or faster with 2 or more cores on a compatible 64-bit processor or System on a Chip (SoC)
2. RAM: 4 GB or greater
3. Storage: 64 GB or larger
4. System firmware: UEFI, Secure Boot capable
5. TPM: Version 2.0
6. Graphics: Compatible with DirectX 12 or later with WDDM 2.0 driver

Pay special attention to TPM 2.0 and Secure Boot, as their absence often causes Windows 11 installation problems.

Sources

1. WinTips.org - FIX: Windows 11 24H2 0XC1900101 - 0x20017 installation error
2. ElevenForum - Windows 11 0xc1900101-0x20017 The installation failed in SAFE_OS phase
3. Tips 2 Fix - 0xC1900101 – 0x20017 Installation failed in SAFE_OS phase
4. UBackup - Fixed: 0xc1900101 0x20017 Windows 11 Installation Error
5. Diskpart - [Solved]Windows Installation Error 0xC1900101 – 0x20017
6. Windows Circle - Fix 0xc19001 0x20017 safe_os windows 11 Error
7. Auslogics - Fixing Installation Failed in Safe_OS Phase with an Error
8. Microsoft Q&A - Azure Windows VM update failed in the SAFE_OS phase
9. Microsoft Q&A - We couldn’t install Windows 11
10. Reddit - r/techsupport on 0xC1900101 – 0x20017 error

Conclusion

• Error 0xC1900101-0x20017 is most often caused by incompatible drivers, so before updating, you need to update all critical drivers to versions compatible with Windows 11.
• Clean boot mode allows you to exclude software and driver conflicts, which often solves the problem of safe Windows 11 installation.
• Using offline installation instead of updating through Windows Update can bypass problems with the update cache and installation components.
• BIOS/UEFI settings play a key role - check that Secure Boot is enabled, TPM 2.0 is enabled, and try temporarily reducing the number of active cores to 1.
• If all methods fail, consider a clean Windows 11 installation followed by restoring data from a backup, as this ensures there are no conflicts with old drivers and system files.