I am having the customer perform a clean boot and blank. I  was just wondering if a reg key setting could 'lock' the volume level...as a possible workaround.

There are no registry keys to lock the volume.

Hi Howard, what exactly does the customer want?  Are they asking for the in call volume, ringer volume, etc? What is the purpose?  Are they trying to set the initial volume? Thanks, Dave

They want the in-call volume to be set at a certain level and not allow for adjustments via the OS.

Hi Howard, I looked up the case notes and see that this customer is really complaining that one unit seems to have the volume go down while others do not.  This wouldn't be anything a registry key can help with.  Even if there is a registry key we can identify, it would only set the initial volume. If this is not that a user has changed things around, I would ask if the volume slider actually shifts downward, or just the audio.  If the volume slider actually goes down to zero then I would guess that either someone is pressing the volume key, or there is a problem with this key sticking or getting recognized by accident. If the volume slider doesn't go down, but audio gets quiet, I would think that points to a hardware issue.