WPF - Low performance when process is executed under SYSTEM account
I think you should bypass the issue altogether. Don't give a system service UI, instead divide your application into two parts - one part that will perform the actual actions will run as a service (under whatever account makes sense) and the other - the UI - will run as an ordinary user process.
Use WCF to communicate between the two relatively easily.
It will solve your performance issue, as well as many potential security issues that your solution exposes.
When a user is logged in, most of the services in your system that are required are up and running. For example whatever you see in taskmanager and system tray.
However, when you run it from the System acc, it has to actually start some of the services that are needed in your case I am guessing it you can solve it by identifying those services and use a different thread altogether which might reduce your turn-around time.
But, the performance and CPU usage will definitely be impacted. I hope this makes sense.Thanks