Location of UEPrereqSetup_x64

After UEPrereqSetup_x64 is installed, if it is ran again, it will say that you can uninstall it, which means it is checking for a location/registry to know if it was installed or not. My question is, where is that location/registry found? I want to be able to check that first along side other stuff that the game require that are not UE related but are needed for the game, to prompt the user for installation. I know that UE does it when the game is launched, but by that time it is too late. I want to have all of them in one place and guide the user how to install them. All this will be done in like a game launcher.