Install as Shared User instead of Single or Service/Protected. Then, remove the BOINCmgr launch icon from the All User Startup folder and put copies in for specific users StartUp folder. If it works with 6 I do not know, but think it will. Specifically the All-User one needs removing else BOINCmgr will start twice which can cause problems.

You do realise that if you use fast switching (windows key+L), that BOINC will keep running and the next user, whatever user will have it running in the background, albeit at the very lowest priority.

let us know if it works.

Not sure why you are deleting a group of threads but perhaps it would be easier on EricaT if you send a list of the threads to WCG via "contacts". That way they can do the all at once and not miss any. Just a suggestion.