Windows - tray icon to all users?

Question

Is it allowed to have some process's icon to be displayed in all user sessions including terminal/multiple local logons, without spawning another process per each session? I don't need to share any windows between session, just the status icon to be able to check service's status without taking additional actions..

Answer 1

Processes can only access the interactive window station and desktops in the same session as the process. So this means you need one process per session.

Answer 2

It's not even possible. Shell_NotifyIcon communicates with a single instance of Explorer.EXE, the one running in the current user context.

Answer 3

I know at least one program that do it - TightVNC server running as a service. You can lookup their sources to understandhow it's done.