Now I'm confused. Administrative privilages have nothing to do with using the GPU. A service process cannot use the GPU, regardless of who owns it, that has nothing to do with F@H, that's just how Windows is designed.

According to the organisation behind F@H , the application requires administrative priviladges to make sure you have the permissions to use the application on the machine. I guess they had enough complaints about people running it when they don't(students, employees etc), so requiring administrative priviladges is the easiest way.

Your explanation though makes sense, even though the solution to the problem it's terrible. I presumed it was for the GPU for weird reasons (bad software, CUDA, somethng like that), but what you described makes the most sense.

Apparently, I managed to get it running today with some magic using icacls and file ownership. The web control does not work, but I'm able to run the Advanced Control Panel and start everything from there.