Error mounting ISO file - "Sorry, there was a problem mounting the file"

Recently, I've had problems using the built in functionality of Windows Explorer to mount ISO files as a virtual DVD drive.  When I tried to mount an iso, there was a long delay with the 'wait' cursor, and eventually I got an error dialog which said simply "Sorry, there was a problem mounting the file."  Subsequent attempts to mount an iso file (whether the same file or a different file) would immediately return the error, without delay.  

I searched far and wide online and could not find a solution that applied in my environment.  Eventually, I tried mounting the iso using the "Mount-DiskImage" powershell command in hopes of getting a more informative error message.  The error I got was:

Mount-DiskImage : A virtual disk support provider for the specified file was not found. 

Searching for that error message lead me to posts about problems installing a device driver.  Then, everything clicked...

Some time ago, we implemented some Device Installation Restriction group policy settings.  By default, installation of any new devices on a computer is blocked, unless it is explicitly listed in the policy as an allowed device.  Since the  Microsoft virtual DVD Rom device wasn't explicitly allowed, it was being blocked by policy.  Normally, when a device fails to install because of this policy windows pops up a toast notification with that info, but it does not in this case.

Adding the device "scsi\cdrommsft____virtual_dvd-rom_" to the list of allowed device ID's resolved this issue and allowed me to successfully mount an iso.  

The moral of the story, if you're using group policy or any software which restricts the installation of devices, this could be causing the failure mounting iso files.  Disable that policy or software temporarily to test, and if that fixes the issue, add the above device ID to your allowed list.  

Hope that helps someone else find the issue a little bit faster than I did!

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