How to fix the “SAFE_OS installation phase failed” error in Windows

If you are trying to update your PC and you encounter the message “The installation failed in the SAFE_OS phase” (often accompanied by the code 0xC1900101 and an operation like BOOT, APPLY_IMAGE, MIGRATE_DATA, etc.), it's perfectly normal to feel a little frustrated. Many users have experienced the same thing when trying to upgrade. Windows 7 u 8 to Windows 10, or of Windows 10 to Windows 11, either with Windows Update, with the Media Creation Tool or with a downloaded ISO.

This error usually appears after the installation wizard seemingly finishes its job, the computer restarts, and instead of continuing with the update, the system reverts to the previous version, displaying the message "failure in the SAFE_OS phase." Behind that message could be conflicting drivers, misconfigured BIOS, external devices, disks with little space, Windows Update errors, problems with Secure Boot, TPM, or even faulty hardware.In this guide you will see, in detail, all the common causes and the most effective methods that have proven useful in real-life situations.

What does the error “SAFE_OS installation phase failed” mean?

During a major Windows upgrade (for example, moving from Windows 10 1909 to 22H2 (or from Windows 10 to Windows 11), the system goes through several internal phases. In the so-called SAFE_OS phaseWindows works in a special installation environment and prepares the new operating system: it applies the image, migrates data, and configures the BootInstall critical updates, etc. If something goes wrong here, you'll see messages like this:

• The Installation failed in the SAFE_OS phase with an error during BOOT operation (0xC1900101 – 0x20017).
• The Installation failed in the SAFE_OS phase with an error during migrate_data operations.
• The Installation failed in the SAFE_OS phase with an error during apply_image operations.
• The Installation failed in the SAFE_OS phase with an error during replicate_os operations.
• The Installation failed in the SAFE_OS phase with an error during install_updates o prepare_first_boot.

These texts indicate at what point in the SAFE_OS phase the installation crashed. It's not always obvious who the exact culprit is, but they do provide some guidance.For example, errors in APPLY_IMAGE often point to disk or graphics problems; errors in BOOT are usually related to drivers, BIOS, or boot configuration; errors in MIGRATE_DATA may have to do with storage hardware or drivers.

Most common causes of the SAFE_OS error in Windows 10 and Windows 11

However technical the error message may sound, in the end it almost always boils down to a handful of typical causes. Many of these issues are repeated time and time again in real-life cases of users experiencing the same error. when trying to install Windows 10 or Windows 11:

1. External devices connected (USB drives, disks, SD cards, printers, etc.)
Any additional peripherals may interfere with the SAFE_OS phase. A simple card reader, a printer, or a USB drive They can cause the installer to malfunction when managing volumes, storage drivers, or data paths. Windows attempts to detect and configure all hardware while preparing the new system, and a problematic device can crash the installation.

2. Faulty, outdated, or incompatible drivers
This is one of the most frequently cited reasons: GPU drivers, network drivers (especially WiFi), card reader drivers (such as some Realtek), storage drivers, etc. A very common real-world example is the error caused by the Realtek card reader driver package. rtsbastor.infwhich causes the update to recent versions of Windows 10/11 to fail. Or the case of Broadcom WiFi cards in some portable Samsung, which blocks the update mid-process.

3. Outdated or misconfigured BIOS or firmware (Secure Boot, UEFI/Legacy)
If the BIOS is in Legacy mode when you need UEFI, or the Secure Boot If it is conflictingly enabled/disabled, the SAFE_OS phase may always fail during the BOOT operation. An old BIOS can also have bugs that manifest themselves when trying to change the Windows version..

4. Disk configuration and Windows 11 requirements (GPT, UEFI, TPM, Secure Boot)
For Windows 11, Microsoft requires certain minimum requirements: disk formatted as GPT, UEFI firmware, TPM 2.0 enabled and secure boot activeIf your PC does not meet this requirement (for example, the system disk is in MBR or TPM is disabled), the installation may refuse to proceed or fail in SAFE_OS.

5. Corrupted Windows Update files or cache
If you are updating via Windows Update and there corrupt files in the update cache, in the BITS service, or in the cryptographic serviceIt's easy for the installation to crash on SAFE_OS. Therefore, a recommended step is to repair Windows Update and configure certain services to start automatically.

6. Lack of space on the system unit or a faulty hard drive
The SAFE_OS phase needs space to apply the new image, copy Temporary files and store a copy of the previous version. If drive C: is at its limit or the mechanical disk has bad sectorsThe process may hang or throw an error during APPLY_IMAGE or MIGRATE_DATA.

7. Conflicting or defective hardware (RAM, graphics card, WiFi, card reader…)
Besides the drivers, some components cause problems on their own. Typical cases: faulty or incorrectly matched RAM modules, incompatible dedicated graphics cards, specific WiFi cards (such as some Broadcom cards in older laptops), and internal card readersIn several documented cases, the update has only worked by physically removing the problematic WiFi or network card.

8. Third-party antivirus and other security programs
Some antivirus programs, firewalls, or security suites interfere too much with the update process. They intercept write operations or modify the boot processAnd that, during SAFE_OS, is the perfect recipe for a 0xC1900101.

Typical error messages and how they differ

Although everyone is talking about the SAFE_OS phase, the messages vary slightly, and that gives clues about what's going on. These are the most common issues encountered when upgrading to Windows 10 or 11.:

"0xC1900101 - 0x20017The installation failed in the SAFE_OS phase during operation BOOT"
This is probably the most famous mistake. It is usually associated with low-level drivers (storage, network, card reader), BIOS, Secure Boot, or attached hardware.Windows fails to boot into the secure environment preparing the new system and reverts the changes.

“The Installation failed in the SAFE_OS phase with an error during APPLY_IMAGE operation"
The failure here occurs when applying the system image to the disk. This could indicate space issues on the C: drive, physical errors in the hard drive/SSD, conflicts with storage controllers, or even with the dedicated graphics card. (Installations have been reported completed by temporarily disabling the dedicated GPU in BIOS and using only the integrated one).

“The Installation failed in the SAFE_OS phase with an error during MIGRATE_DATA/REPLICATE_OS"
These errors appear when Windows tries migrate data from the previous system or replicate the operating system. They are frequently linked to corrupted system files, disk structures that are not entirely clean, or a lack of space to copy data.

“The Installation failed in the SAFE_OS phase with an error during INSTALL_UPDATES o PREPARE_FIRST_BOOT"
Closely related to Windows Update problems, services in incorrect mode, or even faulty ISO downloadsIf the image you're updating with is corrupted, it's very likely that this part will crash.

Quick solutions before diving in deep

Before you start messing with the BIOS, converting disks, or disassembling the laptop, it's a good idea to try a series of simple steps that in many cases are enough to resolve the SAFE_OS error. These are "minimum" measures that you should always apply, both in Windows 10 and Windows 11.:

1. Disconnect all external devices
Turn off the computer and remove absolutely everything that is not essential: external hard drives, USB flash drives, SD cards, printers, USB hubs, mobile phones, USB WiFi cards, etc. If possible, use only a keyboard and mouse, and if they are USB and you have the option, try a PS/2 keyboard/mouse for even more isolation.

2. Free up space on drive C:
Although Microsoft specifies a minimum, in practice it is recommended to have at least 20-30 GB free on the system disk To ensure the update process runs smoothly, remove temporary files, uninstall programs you don't use, and clean up remnants of old Windows installations (Windows.old) if you no longer need them.

3. Run the Windows Update troubleshooter and repair services
In Windows 10 you can use the Windows Update-specific troubleshooterAdditionally, open Run (Win + R), type services.msc and make sure these services are set to "Automatic" startup type:
Background Intelligent Transfer Service (BITS), Windows Update Service, Cryptographic ServiceIf any are set to Manual or Disabled, change them, apply, and accept.

4. Temporarily disable third-party antivirus software
If you use an antivirus other than Windows Defender, temporarily disable it while you perform the updateConsult the developer's website if you can't find instructions. In some extreme cases, it may be necessary to completely uninstall and reinstall the software.

5. Verify that the ISO file or download is legitimate and complete.
If you're using a Windows 11 ISO or a test build, it's crucial to make sure that It is undamaged and comes from an official sourceIdeally, you should download the image from the Microsoft website or use the Media Creation Tool to create a USB drive or a new ISO.

Check if your PC is compatible with Windows 11

In the specific case of Windows 11, a significant portion of "Windows 11 installation failed" errors (including those in the SAFE_OS phase) are due to The equipment does not meet some of the hardware requirementsBefore you continue fighting with the installer, you should check these compatibility points.

1. Basic requirements made official by Microsoft
Your PC must have, at a minimum: Compatible processor, 4 GB of RAM, 64 GB of storage, UEFI firmware, Secure Boot, TPM 2.0 enabled, and system disk formatted as GPTIf you fail in several of these, the cleanest way to enjoy Windows 11 might be to upgrade your hardware.

2. Disk partition type: MBR vs GPT
For Windows 11, The disk where you're going to install the system must be GPTIf you're still using MBR, the installation might fail or break on SAFE_OS. You can check the disk type from within Windows (Disk Management) or with partitioning tools. If necessary, there are programs that allow you to do this. Convert MBR to GPT without losing dataBut it's a good idea to make a backup before touching anything.

3. Boot mode: UEFI and Secure Boot
In your motherboard's BIOS/UEFI, the boot mode should be set to UEFIand in many cases Windows 11 also requires that the Secure Boot is enabledIf you have changed these options in the past (for example, to install older systems), you will probably need to revert them to the modern settings to prevent the Windows 11 installer from complaining.

4. TPM 2.0 enabled
The famous TPM chip It also plays a key role. Many motherboards have TPM or a firmware implementation disabled by default. Enter the BIOS and look for options like “PTT”, “fTPM”, or “TPM 2.0” to enable it. If your computer is very old and doesn't have TPM 2.0, there are Tricks to bypass that requirement, but they already involve unofficial modifications by the installer.

How to fix the SAFE_OS error step by step

Once the basic steps have been completed and compatibility has been verified (in the case of Windows 11), it's time to fine-tune things a bit more. The following techniques are those that have been most frequently used successfully in real-world cases., both when upgrading from Windows 7/8 to Windows 10 and when updating within Windows 10 or making the jump to Windows 11.

1. Disconnect or remove conflicting hardware (WiFi, card reader, dedicated GPU…)
Beyond removing USB peripherals, there are internal devices that should be temporarily disabled:

– Problematic WiFi cards (e.g., Broadcom in some Samsung laptops): In a very common case, the Windows 10 installation from Windows 7 would freeze on the first restart, and when a forced shutdown was attempted, the SAFE_OS error appeared during BOOT. The only effective solution was physically remove the Broadcom WiFi card from the laptop. It wasn't enough to uninstall the driver or disable it from the system; the computer had to be opened and removed.

– Realtek card readers (rtsbastor.inf): Another concrete example is the driver rtsbastor.inf On some computers with a Realtek card reader, you can locate this driver in the Windows driver store and uninstall it using a tool like Driver Store Explorer. After that, the upgrade to Windows 10/11 worked without SAFE_OS errors.

– Dedicated graphics card: If you receive the SAFE_OS error message during the APPLY_IMAGE operation, there is a high probability that the Dedicated GPU doesn't play well with the installerIn that case, enter the BIOS/UEFI, locate the option to disable the dedicated graphics card, and force the use of the integrated graphics. Then, connect the monitor to the integrated graphics output, try the installation again, and once everything is finished, you can reactivate the discrete GPU.

2. Adjust and test the RAM memory
RAM may seem innocent, but defective modules or problematic combinations They can cause crashes right in the SAFE_OS phase. If you suspect this or have performed memory upgrades, try the following:

• Remove the additional modules and leave only a basic module for installation.
• Test the memory with diagnostic tools (MemTest or other utilities).
• Change the slot of the main module if you have several available.

Several users have successfully completed the installation of Windows 10/11 simply by using fewer RAM modules or replacing one that was faulty.

3. Configure critical services in automatic mode
As seen before, if the services BITS, Windows Update, and Cryptographic Service They don't start properly; the update may fail in SAFE_OS, especially in operations related to INSTALL_UPDATES. Open Run > type services.msc > Locate those services > Go into their Properties and set the startup type to Automatic (not just Manual). Save, accept, and restart before trying again.

4. Update system drivers (especially chipset, storage, network, and GPU)
Using very old or generic drivers doesn't always cause problems, but with large updates it's a gamble. You might want to check out:

• Chipset and storage controllers from the website of your motherboard or laptop manufacturer.
• Network driversespecially WiFi and some Ethernet drivers that have caused problems with updates.
• Graphics card drivers, both the integrated (Intel, AMD) as the dedicated (NVIDIA, AMD).

You can use the Device administrator to automatically search for updated drivers or use manufacturer-specific utilities. In systems with many devices, a third-party tool to check all drivers can save you time.However, it is always recommended to download from official sources whenever possible.

5. Check and update the BIOS/UEFI
If your device hasn't had its firmware updated in years, it's worth it. Check the manufacturer's website for a newer BIOS/UEFI version.Sometimes bugs that directly affect compatibility with newer versions of Windows are fixed. Before flashing anything, carefully read the manufacturer's instructions and make sure you don't interrupt the process. While you're at it, take the opportunity to check:

• Make sure the boot mode is UEFI if you are going to install Windows 11.
• Ensure Secure Boot is configured according to your installation's requirements (in some cases, upgrading from Windows 10 may require temporarily disabling it; in others, Windows 11 requires it to be enabled).
• Advanced options such as number of active nuclei (There are systems where temporarily limiting the number of cores to 1 in BIOS has allowed the installation to be completed, and then returning it to its normal value).

6. Repair Windows Update components from within the system itself
When the problem comes from corrupted files in the software distribution folder, in BITS, or in the Windows Update agent itselfIt is recommended to follow Microsoft's official guides for "Repairing Windows Update errors". These usually consist of:

• Temporarily stop update services.
• Rename or clean the SoftwareDistribution and Catroot2 folders.
• Restart services.

Once you've done this, try the update again, either with Windows Update or with the Media Creation Tool.

Install Windows 10/11 without losing files or programs

For many users, the main concern is Don't lose your documents, applications, and settings.Updating “in-place” (from the system itself, keeping files and apps) is the recommended method whenever possible, but the SAFE_OS error can prevent this time and time again.

1. Upgrade from Windows 7 to Windows 10 while keeping license and data
On computers with genuine Windows 7 pre-installed (such as Samsung laptops with Windows 7 Home), the usual thing is to want Upgrade to Windows 10 without losing anythingAs long as the current system is activated, Windows 10 should automatically activate the license during the migration. The correct process is usually as follows:

• Start the update from within Windows 7 using the official tool (Media Creation Tool) or an ISO.
• Make sure Windows 7 is properly activated before starting.
• Choose the option of preserve files and applications.

In some cases, once this initial migration is complete and Windows 10 is verified as activated, you can then proceed to a clean installation after installation Without losing activation, using the same edition of Windows 10 and skipping the product key entry (the system recognizes the digital license). If you encounter SAFE_OS errors during this first update, you'll need to apply all the solutions discussed regarding drivers, BIOS, conflicting hardware, etc.

2. Upgrade within Windows 10 to a higher build (1909 to 22H2, for example)
The idea here is similar: Start the update from the system already bootedNormally, you can do this using the Media Creation Tool or directly through Windows Update. Real-world cases show that some systems running version 1909 no longer offer direct updates, or that the update always fails with SAFE_OS during boot. If this happens to you, you can:

• Manually download the update assistant or the Media Creation Tool from the Microsoft website.
• Create a USB or ISO of the desired version and launch the update from there.
• Apply driver solutions (e.g., remove the conflicting rtsbastor.inf driver using Driver Store Explorer) before trying again.

Once the SAFE_OS obstacle has been overcome, The system updates itself while keeping your apps and data active.unless you choose otherwise in the wizard.

3. When there is no other option but to perform a clean installation
There are situations where, no matter how many adjustments you make, the in-place update still fails. In that case, a clean install from scratch This might be the most sensible option, provided you back up everything important beforehand. On computers that have already had Windows 10/11 activated, the digital license is recovered when you connect to the internet, without needing to re-enter the key, as long as you install the same edition.

Manage disk space and migrate to a faster disk

An old and overloaded hard drive not only slows down the PC; It also makes major updates much more complicated.During the SAFE_OS phase, temporary files are created, backups are made, and images are applied, so the system drive needs space and good health.

1. Expand drive C: to avoid errors due to insufficient space
If your C drive is very tight, you might consider expand it by taking space from other partitionsTo do this, there is partitioning software that allows you to both extend the C drive into unallocated space and reallocate space from other large partitions to C:. The usual steps are:

• If there is unallocated space adjacent to C:, resize C: to occupy it.
• If there isn't any, "steal" space from another partition with plenty of margin and reassign it to C: using the "Allow space" option or similar.

With this, You will drastically reduce the probability of the SAFE_OS phase running out of space and failing..

2. Migrate the system to a new SSD
If the mechanical hard drive is old or shows signs of failure, consider migrating the system to a Modern SSDA good plan might be:

• Clone your current system from your HDD to your SSD using a migration tool.
• Boot from the SSD and check that everything is working.
• Upgrade to Windows 10/11 from the new hard drive, where reading/writing will be much faster and more stable.

Many update problems that seemed mysterious disappear when the system operates on a disc in good condition and with plenty of space.

After reviewing all these causes and solutions, it becomes clear that the error “SAFE_OS installation phase failed” is not a single problem but a set of situations that converge in the same message: Conflicting drivers, faulty hardware, outdated BIOS, unmet Windows 11 requirements, insufficient or damaged disk space, and malfunctioning Windows Update servicesBy acting systematically—disconnecting peripherals, checking compatibility, correcting services, updating or removing problematic drivers, adjusting RAM and GPU, ensuring GPT, UEFI, Secure Boot and TPM for Windows 11 and taking care of the disk's health—the vast majority of users finally manage to complete the upgrade without losing their files or programs, leaving this troublesome error behind forever.