I run BOINC 6.10 together with COLLATZ (GPU Computing) on XP
Unfortunately all other users on the machine check for BOINC presence in the tray and deactivate boinc
I set the Icon to allways hidden, that is stored, but the icon is still shown.
Any ideas? Boinc is not runing as service

You don't say what OS you're using, but if it's Windows, then un-install BOINC and re-install, checking for a button labelled Advanced. (It was on the 3rd install screen; not sure if it still is.)

On this extra page, make sure that the option for All users to <access? run? control?> BOINC is NOT ticked.
Then be sure to log out of your Windows account before leaving the computer.
Not sure, but you may also need to install as a service for this to work.

But the end result will be that only YOU can see/access/change BOINC.

Boinc is divided into two parts, the Boinc client (hidden) and the Boinc Manager (the GUI),
the way to do it, is to allow them to shut the manager down, but leave the client and science apps running,
So go to: Advanced>Options, tick 'Enable Manager exit dialog?', then O.K,
Now go: File>Exit, Untick 'Stop running science applications when exiting the Manager',
and Tick 'Remember this decision and do not show this dialog', then Click O.K,
Now the GUI has been shut down, but the client and apps are still running in the background.

When you Do want to shut down the client and the science apps,
go: Advanced>Options, tick 'Enable Manager exit dialog?', then O.K,
then: File>Exit, Tick 'Stop running science applications when exiting the Manager', then O.K.

Claggy

Edit: or you can install it as a Service.