Error “Sorry, there was a problem mounting the file”

When you double-click on an ISO file to mount it to a drive-letter, nothing may happen except the hourglass cursor. After 5 minutes or so, the following error appears:

Couldn't Mount File

Sorry, there was a problem mounting the file.

cannot mount iso

Note: If you receive a different error message (“You don’t have permission to mount the file”), it’s a different issue. See the Microsoft Docs GitHub article for the fix.


The above error occurs if CDROM filter driver is referenced in the registry, but the driver file is missing. This prevents the ISO images from being mounted.


To resolve the issue, delete the third-party filter driver references for the CDROM class from the Windows registry.

  • Start the Registry Editor (regedit.exe)
  • Go to the following location:
  • Delete the two values, namely “LowerFilters” and “UpperFilters”.
  • Exit the Registry Editor.
  • Restart Windows and see if you’re able to mount ISO images.

Additional Information

For example, the above error may occur after deleting the PxHlpa64.sys driver and its service registration to enable the Memory Integrity feature. However, the LowerFilters or UpperFilters registry entry is usually left over after deleting the service. PxHlpa64.sys is part of the PxEngine library, used by Roxio products for burning optical discs.

See also

Fix: Cannot Enable Core Isolation Due to Incompatible Drivers

You cannot enable the Windows Memory Integrity feature because PxHlpa64.sys is not compatible

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Ramesh Srinivasan is passionate about Microsoft technologies and he has been a consecutive ten-time recipient of the Microsoft Most Valuable Professional award in the Windows Shell/Desktop Experience category, from 2003 to 2012. He loves to troubleshoot and write about Windows. Ramesh founded in 2005.

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