I have a new hardware device installed and since installing it unused icons in the notification area no longer are hidden. I tried resetting with ERUNT, but I had to install the software again, with the same result.
The device is a digital/analogue/fm TV and radio receiver, that also operates as a video capture device, and it places an icon in the notification area. Whether that is relevant or not I am not sure but I want my little arrow back.


