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If Windows reports that mrxsmb10.sys is missing or cannot be found, repair the Windows component store and protected system files rather than downloading a replacement from the internet. Install pending updates, run DISM.exe /Online /Cleanup-image /Restorehealth in an elevated Terminal or Command Prompt, then run sfc /scannow and restart. DISM repairs the source Windows uses for system files; System File Checker then verifies and replaces protected files in the running installation.
MRXSMB10.SYS is part of the Windows SMB client and normally resides in %windir%System32Drivers. The error does not, by itself, mean that SMBv1 must be enabled. If the built-in repair sequence cannot obtain files from Windows Update, use matching Windows installation media as a DISM source. Escalate to Windows recovery or a reinstall only after those supported repairs fail.
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What is mrxsmb10.sys, and why does Windows need it?
MRXSMB10.SYS is a Microsoft SMB (Server Message Block) client binary. Microsoft’s file list places it in %windir%System32Drivers with other SMB and redirector components, including RDBSS.sys, MRXSMB.sys, MRXSMB20.sys, MUP.sys and SMBdirect.sys. These components allow Windows to communicate with shared folders, file servers and other SMB resources.
A “missing,” “not found” or “Windows cannot find mrxsmb10.sys” message means the operating system cannot access a protected component it expects. The cause can be corruption in the component store, an interrupted update, disk or file-system damage, or a damaged Windows installation. Microsoft Support warns: “When critical Windows system files are missing or corrupted, your operating system may begin to malfunction.” The message identifies a system-file problem; it does not prove that a particular network share, game, server or account is at fault.
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Is mrxsmb10.sys the same thing as SMBv1?
No. The file is an SMB client component, but seeing its name is not proof that the legacy SMBv1 protocol should be installed or enabled. Microsoft Learn states that “The SMBv1 network protocol is no longer installed by default.” A missing-file report should therefore be handled as Windows component corruption first, not as an instruction to turn on an older protocol.
Do not enable SMBv1 merely to clear this message. First repair Windows with DISM and SFC. Revisit protocol compatibility only if a separate, documented application or server requirement remains after the file-repair problem is resolved.
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The commands below repair the Windows installation that is currently running. Save open work, connect the computer to reliable power, and use an account that can approve administrator prompts.
- Confirm whether the affected installation is Windows 10 or Windows 11 and note its edition and display language. You will need those details if an alternate repair source is required.
- Disconnecting from a metered or unreliable network is not necessary, but DISM normally obtains repair files through Windows Update, so a working internet connection helps.
- Do not download
mrxsmb10.sysfrom an unrelated file repository or copy a file from a different Windows release. A mismatched binary can leave the component store inconsistent. - If the error appeared immediately after an update or forced shutdown, postpone nonessential troubleshooting until the update has completed and Windows has restarted.
How do I repair mrxsmb10.sys on Windows 11 or Windows 10?
Use this order: update and restart, run DISM, run SFC, then restart and test the operation that produced the message. Microsoft’s guidance places DISM before System File Checker because SFC depends on a healthy component source.
1. Install pending Windows updates and restart
- Open Settings.
- In Windows 11, choose Windows Update. In Windows 10, choose Update & Security, then Windows Update.
- Select Check for updates and install all available updates. Follow any restart prompt.
- After Windows starts again, retry the action that originally produced the error. If the message remains, continue with DISM.
Updating first matters because DISM normally uses Windows Update as its repair source. A restart also finishes servicing operations that can otherwise leave files temporarily unavailable.
2. Open an elevated Command Prompt or Windows Terminal
- Right-click the Start button, or press
Windows+X. - Select Terminal (Admin), Windows PowerShell (Admin) or Command Prompt (Admin), depending on the labels shown by your Windows build.
- Approve the User Account Control prompt. The window title should indicate administrator privileges.
If the menu does not offer an administrator entry, search for Command Prompt or Windows Terminal, right-click the result and choose Run as administrator.
3. Run DISM to repair the component store
Enter this command exactly, including the spaces and forward slash characters:
DISM.exe /Online /Cleanup-image /Restorehealth/Online targets the Windows installation currently running. /Cleanup-image selects component-store servicing, and /Restorehealth asks DISM to detect and repair corruption. The process can take several minutes, and the percentage may pause for a while. Leave the window open until DISM reports completion.
A successful completion message means DISM finished its requested repair. It does not replace the next step: Microsoft says, “You should run DISM prior to running the System File Checker.” If DISM reports that it cannot find source files, stop and use the alternate-source procedure below instead of repeatedly running the same command.
4. Run System File Checker
In the same administrator window, run:
sfc /scannowSFC checks protected files in the running Windows installation and replaces damaged copies when a valid component source is available. Do not close the window or restart while verification is in progress; wait until it reaches 100 percent and displays a result.
5. Restart and test the original operation
- Close the administrator window after SFC has finished.
- Restart Windows from Start > Power > Restart.
- Repeat the file-sharing, application or network operation that showed the
mrxsmb10.sysmessage.
A restart loads repaired drivers and completes pending servicing actions. If the error is gone, no SMBv1 change is needed.
What if DISM says it cannot find the source files?
When Windows Update is unavailable or its repair files are damaged, Microsoft documents using a working Windows installation as an alternate source. The source can be a matching network share, USB drive or DVD. It must match the installed Windows version, edition and language; media from another release or edition can produce a new servicing error.
Prepare a matching source
- Use installation media created for the same major Windows version as the affected installation.
- Match the edition, such as Home or Pro, and the display language.
- Use a source that contains the Windows files and is readable from the affected computer. A network share must remain available for the entire command.
- Identify the actual Windows folder on the media or share. Do not guess a drive letter or folder name; it can differ between computers.
Run DISM with the source and prevent Windows Update fallback
Replace the example path with the real Windows directory on your media or share:
DISM.exe /Online /Cleanup-Image /RestoreHealth /Source:\serverc$windows /LimitAccess/Source tells DISM where to obtain repair files. /LimitAccess prevents it from trying Windows Update, which is useful when that service is unavailable or the source is known to be damaged. The example uses a network share; a USB or DVD path must be written using the drive letter and folder that actually contain the installation files.
After DISM completes successfully, run sfc /scannow again, restart, and test the original operation. If the alternate source is rejected, verify the version, edition, language and path before trying again. Do not mix files from different media simply because they have similar names.
How can I interpret the SFC result?
SFC normally ends with one of several messages. The wording determines what to do next.
- Windows Resource Protection did not find any integrity violations: SFC found no protected-file corruption in the running installation. Restart if you have not already done so, then investigate the specific application or network operation that still fails.
- Windows Resource Protection found corrupt files and successfully repaired them: Restart Windows and retry the operation. The repaired component may not be loaded until the restart.
- Windows Resource Protection found corrupt files but was unable to fix some of them: Run DISM again, making sure it completed successfully and used a matching source if necessary, then run SFC once more. If unresolved corruption remains, move to recovery options rather than copying random files.
Extract the detailed SFC entries
To create a readable report on the desktop, run this command in an administrator Command Prompt:
findstr /c:"[SR]" %windir%LogsCBSCBS.log >"%userprofile%Desktopsfcdetails.txt"Open sfcdetails.txt and review its newest entries. The complete servicing log remains at %windir%LogsCBSCBS.log. The report can show which protected files SFC examined and whether a repair was attempted; it does not replace the need to use a valid component source.
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Use the least disruptive supported method that matches the failure. DISM and SFC are built into Windows and should be attempted before recovery or reinstalling.
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| Method | What it repairs | Repair source | When to use it | Risk and effort |
|---|---|---|---|---|
DISM with /Online |
The Windows component store that supplies protected files | Usually Windows Update | First command after updates and a restart | Built in; can take several minutes and needs administrator rights |
| SFC | Protected files in the running Windows installation | The repaired local component store | After DISM completes | Built in; do not interrupt verification |
DISM with /Source and /LimitAccess |
The component store, using external installation files | Matching USB, DVD or network installation files | When Windows Update cannot provide repair files | Still supported, but source version, edition and language must match exactly |
| Windows recovery options or reinstall | The broader Windows installation | Recovery environment or installation media | When DISM and SFC cannot repair the component | Greater disruption; back up important data and follow Microsoft’s recovery guidance |
What common mistakes prevent the repair?
Running SFC before DISM
SFC may report that it cannot repair files when the component store itself is damaged. Run DISM first, allow it to finish, and then repeat SFC.
Closing a command window during a pause
DISM and SFC can hold at one percentage for several minutes. A pause is not proof that the process has stopped. Interrupting it can leave servicing incomplete, so wait for a final status message.
Using an unmatched USB or DVD
A source from a different Windows version, edition or language may not contain the correct component versions. Confirm those attributes before specifying /Source.
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Guessing the source path
The media may use a different drive letter or folder layout than the example. Check the mounted drive or share and point DISM to the directory that actually contains the Windows files.
Assuming the message proves an SMBv1 requirement
MRXSMB10.SYS belongs to the SMB client stack, but the error alone does not establish that the legacy protocol is needed. Repair the file and component store first; only investigate protocol compatibility if a separate service or server documents that requirement.
Replacing a system file with an arbitrary copy
A file copied from another computer can have a different build, servicing state or permissions. Microsoft’s supported path is component repair; manual replacement is appropriate only with a known-good copy from a matching Windows installation and Microsoft’s ownership and permission instructions.
When should I use recovery options or reinstall Windows?
If a correctly sourced DISM repair and a subsequent SFC scan still leave the component missing or corrupted, Microsoft Support says Windows recovery options or a reinstall may be necessary. Before choosing a reset or reinstall, back up personal files and record application installers, network settings and encryption-recovery information that you may need afterward.
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Frequently asked questions
Can I safely delete mrxsmb10.sys and let Windows recreate it?
No. It is a protected Windows component, and deleting it can create additional startup or networking problems. Repair the component store and protected files with DISM and SFC instead.
Will enabling SMBv1 restore the missing file?
There is no basis to assume that it will. SMBv1 is not installed by default on current Windows versions, and a missing-file message should be repaired as a Windows component problem before any protocol-compatibility decision.
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Both commands can take several minutes, and progress can appear to stop temporarily. The reliable stopping point is the final completion or error message, not a percentage that remains unchanged.
What if Windows cannot boot normally after the error?
Use Windows recovery options to reach supported repair tools. If recovery cannot repair the installation, Microsoft’s guidance allows escalation to reinstalling Windows after protecting your personal data.
Is copying mrxsmb10.sys from another PC ever safe?
Only a known-good copy from a matching Windows installation, handled with Microsoft’s ownership and permission instructions, is an appropriate manual-replacement scenario. A random download or a file from a different build can make servicing and future updates less reliable.
Frequently Asked Questions
Can I safely delete mrxsmb10.sys and let Windows recreate it?
No. It is a protected Windows component, and deleting it can create additional startup or networking problems. Repair the component store and protected files with DISM and SFC instead.
Will enabling SMBv1 restore the missing file?
There is no basis to assume that it will. SMBv1 is not installed by default on current Windows versions, and a missing-file message should be repaired as a Windows component problem before any protocol-compatibility decision.
How long should DISM and SFC take?
Both commands can take several minutes, and progress can appear to stop temporarily. The reliable stopping point is the final completion or error message, not a percentage that remains unchanged.
What if Windows cannot boot normally after the error?
Use Windows recovery options to reach supported repair tools. If recovery cannot repair the installation, Microsoft’s guidance allows escalation to reinstalling Windows after protecting your personal data.
Is copying mrxsmb10.sys from another PC ever safe?
Only a known-good copy from a matching Windows installation, handled with Microsoft’s ownership and permission instructions, is an appropriate manual-replacement scenario. A random download or a file from a different build can make servicing and future updates less reliable.
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