A growing number of Macrium Reflect 8 users have reported problems mounting backup images after recent Windows 11 security updates.

The issue centers on a vulnerable driver called psmounterex.sys, which Macrium Reflect 8 uses to mount backup images as virtual drives so users can browse backed-up files in File Explorer. Once Windows blocks that driver, the image-mounting feature can fail even though the backup image itself may still exist and rescue media may still be able to restore it.

Macrium Reflect 8 Free: No Longer Supported

The complaints are especially concerning for Macrium Reflect 8 Free users because Reflect 8 is no longer being actively updated. Microsoft is treating the driver block as a security hardening change, not as a Windows Update mistake that will simply be reversed. Macrium says Reflect 8 and Reflect LTSC are affected by the confirmed image-mounting issue, while Reflect X is not affected because it does not use psmounterex.sys. (Source: macrium.com)

There is a registry workaround that can temporarily restore image mounting by disabling the Microsoft Vulnerable Driver Blocklist, but that workaround also weakens a Windows security protection system-wide. That makes it a short-term recovery option, not a proper long-term fix. Macrium Reflect 8 Free users who rely on image mounting should start planning for a supported backup product or a supported Macrium version instead of assuming the workaround will remain safe or permanent.

What Actually Broke?

The problem is not that Windows Update randomly broke Macrium Reflect. The problem is that Windows is now refusing to load a driver that Macrium Reflect 8 depends on for a specific feature: mounting backup images inside Windows so you can browse them like a virtual drive.

That distinction matters. In many cases, your existing backup images may still be valid. Your rescue media may still work. Your full image backups may still be restorable. The part that is most clearly affected is the ability to open a Macrium image file inside Windows and assign it a drive letter so you can browse files through File Explorer.

For users who rely on Macrium Reflect 8 Free, this is a serious problem. The free version has already been discontinued, and Macrium Reflect 8 itself is now end-of-life. That means users should not expect a normal free update that replaces the affected driver and restores long-term compatibility.

Why Did Microsoft Block psmounterex.sys?

Windows uses kernel drivers for low-level access to the operating system. Backup programs often need this type of access because they work with disks, snapshots, partitions, file systems, and image files. That power is useful, but it also creates risk. If a kernel driver has a serious vulnerability, malware can potentially abuse it to gain higher privileges or tamper with the system.

Microsoft's vulnerable driver blocklist is designed to stop known vulnerable drivers from loading. In this case, Microsoft added vulnerable versions of psmounterex.sys to the blocklist. Once that happened, Windows Code Integrity enforcement began blocking the driver from loading when the vulnerable driver blocklist is enabled.

This is why the issue can appear suddenly after an update. Macrium Reflect 8 may not have changed at all. The driver may still be present on disk, but Windows now refuses to load it.

Does This Mean Your Backups Are Useless?

The confirmed driver block affects image mounting. That means the feature used to mount a backup image as a virtual drive inside Windows may fail. It does not necessarily mean every backup image you created is corrupt. It also does not necessarily mean you cannot restore your system using rescue media.

Macrium says backup creation and image restores continue to function in relation to the confirmed image-mounting issue. That said, if you are seeing separate VSS errors, failed backup jobs, or snapshot creation problems, you should treat that as a separate reliability issue and verify your backups immediately.

The practical advice is simple: do not assume your backups are good. Test them. Create rescue media. Boot from it if possible. Confirm that your backup destination is visible. Confirm that your image files are detected. A backup program that says "success" is useful, but a tested restore path is better.

The Registry Workaround

There is a registry workaround that disables the Microsoft Vulnerable Driver Blocklist. This may allow Macrium Reflect 8 to load psmounterex.sys again and restore image-mounting functionality, at least for now.

Open Command Prompt as Administrator and run:

Then restart the computer.

To turn the vulnerable driver blocklist back on later, run:

Then restart the computer again.

Why the Registry Workaround is Risky

The registry workaround is not a Macrium-only exception. It does not say, "Allow Macrium Reflect but keep blocking other dangerous drivers." Instead, it turns off the Microsoft Vulnerable Driver Blocklist setting.

That is a much broader security change. The blocklist exists because attackers abuse vulnerable drivers to get kernel-level access. Disabling it may allow other known vulnerable drivers to load, not just psmounterex.sys. That is why this workaround should be treated as temporary and situational, not as a permanent fix for every user.

If you only need to mount one old backup image to recover files, one safer approach is to temporarily disable the blocklist, restart, mount the image, extract the files you need, then re-enable the blocklist and restart again. That still carries risk, but it limits how long the machine runs with the protection disabled.

If this is a business system, server, or machine exposed to high-risk activity, disabling driver protection is harder to justify. In that case, the better answer is to update the backup software or use a supported recovery path.

Will Microsoft Fix This?

Users should not assume Microsoft will reverse this change. Microsoft describes the behavior as intentional security hardening. It says psmounterex.sys will remain on the vulnerable driver blocklist, and that applications depending on the driver will continue to experience failures until they are updated to a newer version that includes the required protections.

That is the key point: Microsoft is not treating this as a simple Windows bug that will be undone in the next cumulative update. From Microsoft's point of view, blocking vulnerable kernel drivers is the fix. If older backup software depends on a blocked driver, the software needs to change.

Will Macrium Reflect 8 Free Be Updated?

This is where Macrium Reflect 8 Free users are in a difficult position. Macrium Reflect Free was already discontinued, and Macrium Reflect 8 is now considered end-of-life. Macrium's own guidance points Reflect 8 customers toward upgrading to Reflect X where possible.

That means a free Reflect 8 user should not expect a long-term software update that permanently resolves this in the same product line. There may be temporary workarounds, and some existing backup and restore features may continue to work, but the long-term direction is clear: the old driver model is being blocked, and the old free product is not being actively developed.

For users who want to stay with Macrium, the practical upgrade path is Reflect X. For users who do not want a paid Macrium upgrade, the practical alternative is to move to another backup product that is actively maintained and does not depend on the blocked driver.

Will the Workaround Keep Working?

Maybe, but you should not build your backup strategy around it.

The registry workaround may work today on some systems because Windows still allows the vulnerable driver blocklist to be disabled. However, there are several reasons it may not remain dependable. Future Windows updates could change enforcement behavior. Enterprise policy could override the setting. Memory Integrity, Smart App Control, Secure Boot, or other security controls may affect whether the driver can load. Microsoft could also tighten driver enforcement further if it decides the risk is too high.

Even if the workaround continues to work, it leaves you with a security trade-off. You are weakening a Windows protection layer so that an older backup product can keep using a blocked driver. That may be acceptable for a short recovery task. It is not ideal as a permanent backup plan.

Conclusion

The Macrium Reflect 8 problem after recent Windows updates is not a generic update glitch. Microsoft intentionally blocked vulnerable versions of psmounterex.sys, a kernel driver used by Reflect 8 for image mounting. That can break the ability to mount backup images as virtual drives, even if the backup files themselves are still valid.

The registry command to disable the vulnerable driver blocklist may restore functionality temporarily, but it weakens Windows driver protection system-wide. It should be used carefully, preferably only long enough to recover files from an image, and then reversed.

For Macrium Reflect 8 Free users, the hard truth is that the product is no longer a dependable long-term fit for current Windows security enforcement. If image mounting matters to your workflow, the real fix is not waiting for Microsoft to undo the block. The real fix is moving to backup software that is still maintained and uses a driver model Windows will continue to accept.