Fixing a customer problem: “No Audio Device is Installed” when launching sndvol on Windows Vista

Yesterday someone forwarded me an email from one of our DirectShow MVPs – he was having problems playing audio on his Windows Vista machine.


Fortunately David (the MVP) had done most of the diagnostic work – the symptoms he saw were that he was receiving a “No Audio Device is Installed” error launching sndvol (and other assorted problems). 

David tried the usual things (confirming that the driver for his audio solution was correctly installed (this probably fixes 99% of the problems)).  He also tried reinstalling the driver to no avail.

He next ran the Sysinternals Process Monitor tool to see what was going on.  He very quickly found the following line in the output from process monitor:

"RegOpenKey", "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\MMDevices\Audio\Render\{e4ee1234-fc70-4925-94e9-4117395f7995}", "ACCESS DENIED", "Desired Access: Write"

With that information, he looked for the ACL on that registry key:


He then looked at the configuration for the Windows Audio service:


Woah – the Windows Audio service doesn’t have access rights to that registry key – the Windows Audio service is running as LocalService and the LocalService account doesn’t have any access to the registry key.

At this point he decided to contact Microsoft with his problem.

I looked at his info and quickly realized that the problem was that somehow the ACL on the registry key had been corrupted: something had removed the entries for the audio services.  On a normal Windows Vista installation this registry key’s ACL should look something like:


Something that ran on David’s machines went in and reset the permissions for this registry key to the ACL that is on the root node of the HKEY_LOCAL_MACHINE\Software registry hive.  I have no idea what did this, but messing with the ACLs on the registry is a known cause of various compatibility problems.  That’s why Microsoft KB 885409 has such strong warnings about why it’s important to not apply blind modifications to files or registry keys in Windows.  It’s unfortunate, but the warnings in the KB articles that say that modifying registry keys or permissions can cause your machine to malfunction are absolutely right – it’s not hard to make modifications to registry keys that can really screw up a machine, if you make the right ones.  From the KB article:

For example, modifications to registry ACLs affect large parts of the registry hives and may cause systems to no longer function as expected. Modifying the ACLs on single registry keys poses less of a problem to many systems. However, we recommend that you carefully consider and test these changes before you implement them. Again, we can only guarantee that you can return to the recommended out-of-the-box settings if you reformat and reinstall the operating system.

The good news is that it should be relatively simple to fix David’s problem – As far as I know, he has two options.  The first is to reinstall Windows Vista – that should reset the ACLs on the property key to their default values (because it will recreate the property keys), which should resolve the problem.

The second solution is to add an ACL to the registry keys under the MMDevices registry key to allow the LocalService account to have permissions to modify this registry key.