Logitech mouse huh. Bit off topic but thought I'd share...
Dr calls - cannot change the volume in Windows. I VNC to his PC and change the volume - lower it. It moves itself back to full volume

Dr also reports green text on his screen - something about master volume. He's tried adjusting the settings on the screen and switching it off/on. Still the green text. The monitor is a Fujitsu - they don't have green text. It's an X-File, methinks. They're here at last
Turned out it was the + volume button on his Logitech mouse - was accidentally pressed