Experience Firefly Studios’ award-winning video games, including the classic RTS castle sim Stronghold series, Stronghold Kingdoms and Stronghold Crusader 2. Check out the latest here and play now! I tried to install Stronghold 2 but Installshield wont let me. I have installed it on other computers but this new one doesn't accept it. Error: (-5006: 0X80070020) has occurred while running set up. Thank You, Mike.