If the setup keeps popping up when trying to start the game, then you do not have enough privileges to change the Windows registry. Unfortunately, the client reads those settings (resolution, etc.) from the registry, so neither opensetup.exe nor setup.exe can fix this problem as they're unable to write any values into the registry.
So if you want to be able to play, you must have administrator access to the computer, or it's not possible to do so. I know this means that you might not be able to play while at school. Maybe there's a program to fake the registry that I am not aware of, but without such a thing, not possible.