Fix: This File Came From Another Computer Warning October 2025

Have you ever tried to open a file on your Windows computer, only to see a warning that says “this file came from another computer and might be blocked to help protect this computer”? This frustrating message can stop you from accessing important documents, programs, or media files.

The good news is that this isn’t actually an error, it’s a security feature designed to keep your computer safe from potentially harmful files. In this comprehensive guide, you’ll learn exactly why this warning appears and multiple ways to fix it, from quick unblocks to permanent solutions.

Key Takeaways

• The “this file came from another computer and might be blocked” message is a Windows security feature, not an error
• Windows adds a Zone Identifier to files downloaded from external sources to mark them as potentially untrusted
• You can unblock individual files through Properties or use PowerShell for multiple files
• For permanent solutions, you can disable Protected View in Office, use Group Policy Editor, or edit the Registry
• Always verify file safety before unblocking, as this feature protects against malware
• Network-shared files often trigger this warning due to Windows security policies

What Does “This File Came From Another Computer and Might Be Blocked” Mean?

When you see the message “this file came from another computer and might be blocked to help protect this computer,” Windows is telling you that the file has been marked as potentially untrusted.

This happens because of a Windows security feature called the Attachment Manager, which adds special metadata called a “Zone Identifier” to files that come from outside your computer.

You’ll typically encounter this warning when:

• Downloading files from the internet using browsers like Chrome, Edge, or Firefox
• Receiving email attachments in Outlook or other email clients
• Copying files from USB drives, external hard drives, or network shares
• Transferring files between different computers

The Zone Identifier is like a digital sticky note that tells Windows, “Hey, this file came from somewhere else, so be careful before opening it.” While this feature helps protect your computer from malware and viruses, it can be annoying when you know the file is safe. According to Microsoft’s official documentation, this is part of Windows’ defense-in-depth security strategy.

How to Unblock Files from Another Computer?

If you need to access a file that’s been blocked, you have several options depending on how many files you need to unblock and how comfortable you are with technical solutions.

Method 1: Manual Unblock via File Properties (Easiest Method)

This is the simplest way to unblock individual files:

1. Right-click on the blocked file
2. Select “Properties” from the menu
3. Look for the “Security” section at the bottom of the General tab
4. Check the box that says “Unblock”
5. Click “Apply” then “OK”

The file will now be unblocked, and the warning message won’t appear again for that specific file. This method works perfectly when you only have a few files to unblock.

Method 2: Using PowerShell for Multiple Files

If you have many blocked files in a folder, using PowerShell is much faster:

1. Press Windows + R to open the Run dialog
2. Type “powershell” and press Ctrl + Shift + Enter to run as administrator
3. Type this command and press Enter:
4. Line Wrapping
5. Collapse
6. Copy
7. dir C:\Users\[YourUsername]\Downloads -Recurse | Unblock-File
8. Replace the path with the location of your blocked files

This command will unblock all files in the specified folder and its subfolders. It’s a powerful tool when you need to unblock files from another computer in bulk.

Method 3: Using Microsoft Streams Tool

For advanced users, Microsoft provides a tool called Streams that can remove the Zone Identifier data:

1. Download the Streams tool from the official Microsoft website
2. Open the tool and navigate to the folder with blocked files
3. Click “Scan” to see all data streams
4. Find entries marked “:Zone.Identifier:$DATA”
5. Right-click and select “Delete Selected Streams”
6. Restart your computer

This method directly removes the metadata that causes the blocking warning.

How to Disable “This File Came From Another Computer Blocked” Warning?

If you’re tired of seeing these warnings frequently, you can disable them entirely. However, remember that this reduces your computer’s security protection.

Method 1: Disable Protected View in Microsoft Office

For Office files specifically, you can turn off Protected View:

1. Open any Office program (Word, Excel, etc.)
2. Click on “File” > “Options”
3. Select “Trust Center” then click “Trust Center Settings”
4. Choose “Protected View” from the left menu
5. Uncheck “Enable Protected View for files originating from the Internet”
6. Uncheck “Enable Protected View for Outlook attachments”
7. Click “OK” to save changes

This will [opening these files might be harmful disable] for Office documents only. As Microsoft explains, Protected View is a read-only mode that prevents potentially dangerous content from running.

Method 2: Use Group Policy Editor

This method disables the feature system-wide but only works on Windows Pro, Enterprise, or Education editions:

1. Press Windows + R and type “gpedit.msc”
2. Navigate to: User Configuration > Administrative Templates > Windows Components > Attachment Manager
3. Find “Do not preserve zone information in file attachments”
4. Double-click it and select “Enabled”
5. Click “Apply” then “OK”
6. Restart your computer

This will prevent Windows from marking future downloaded files with the “from another computer” flag, effectively solving the [this file came from another computer disable] issue.

Method 3: Edit Windows Registry

For Windows Home edition users or if Group Policy isn’t available:

1. Press Windows + R and type “regedit”
2. Right-click Registry Editor and select “Run as administrator”
3. Navigate to: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies
4. Right-click “Policies” > New > Key
5. Name the new key “Attachments”
6. In the right pane, right-click > New > DWORD (32-bit) Value
7. Name it “SaveZoneInformation”
8. Double-click it and set the value to “1”
9. Click “OK” and restart your computer

Warning: Editing the Registry can be dangerous. Always create a restore point before making changes. If you’re not comfortable with this, check out our guide on Windows security settings for safer alternatives.

Is It Safe to Disable “Opening These Files Might Be Harmful” Warnings?

When you see a message that [windows found that this file is potentially harmful], it’s important to consider the security implications before disabling these warnings.

These warnings exist for good reason, they protect you from malware, viruses, and other security threats. However, they can sometimes be overly cautious, especially with files from trusted sources.

When it’s generally safe to unblock:

• Files from reputable websites and official sources
• Documents you created yourself on another computer
• Files shared by trusted colleagues or family members
• Software from well-known developers

When to be extra careful:

• Files from unknown websites or email attachments
• Executable files (.exe, .msi, .bat)
• Files shared in public forums or social media
• Anything that seems suspicious or unexpected

A good practice is to scan files with Windows Security or your antivirus software before unblocking them. You can learn more about file security best practices from Microsoft’s documentation.

Why Windows Found That This File Is Potentially Harmful?

Windows uses several methods to determine if a file might be harmful:

1. File Origin: Files from the internet, email attachments, or network locations are automatically flagged
2. File Type: Executable files, scripts, and macros get extra scrutiny
3. SmartScreen Filter: Microsoft’s cloud-based reputation system checks files against a database of known threats
4. Digital Signatures: Files without valid digital signatures from trusted publishers are considered riskier

Sometimes, Windows makes mistakes and flags safe files. This is called a “false positive” and commonly happens with:

• Custom scripts or macros you’ve written yourself
• Files from internal company networks
• Older software that hasn’t been updated recently
• Files from smaller developers who haven’t paid for digital certificates

If you’re experiencing frequent false positives, you might want to check your Windows Security settings or consider adding trusted locations to your exceptions list.

How to Unblock Files Copied from Network?

Files copied from network drives or shared folders often trigger the “this file came from another computer and might be blocked” warning more frequently than other sources. This is because networks, especially in business environments, can be sources of security threats.

To [unblock files copied from network], you have several options:

For Individual Files:

Use the manual unblock method described earlier by right-clicking the file, selecting Properties, and checking the Unblock box.

For Multiple Network Files:

1. Map the network drive to a letter on your computer
2. Use the PowerShell method mentioned earlier, pointing to the mapped drive
3. Or use the Group Policy or Registry methods to disable the feature entirely

In Enterprise Environments:

If you’re in a business setting, your IT department may have security policies that prevent you from unblocking files. In this case:

• Contact your IT department for assistance
• They may add trusted network locations to a safe list
• Or they might provide a tool to safely unblock files

Network security is important, especially in business environments. If you’re dealing with network security issues, you might find our article on secure boot settings helpful for understanding other security features.

Frequently Asked Questions

Conclusion

Dealing with the “this file came from another computer and might be blocked to help protect this computer” warning can be frustrating, but now you have multiple solutions at your disposal. From quick manual unblocks for individual files to permanent system-wide changes, you can choose the method that best fits your needs and comfort level.

Remember that this security feature exists to protect you from real threats, so always verify file safety before unblocking. For most users, the manual unblock method through file properties is sufficient for occasional needs. If you frequently transfer files between computers or download from trusted sources, the PowerShell method or Group Policy changes might be more convenient.

Whatever method you choose, make sure you’re making informed decisions about your computer’s security. When in doubt, scan files with Windows Security or your antivirus software before unblocking. For more Windows security tips and troubleshooting guides, check out our other articles on network security and system protection.

Have you found these solutions helpful? Do you have any other questions about Windows file security? Let us know in the comments below!