Ok, fould out that MO must run as administrator or the "access denied" error will popup But Fallout 3 itself has a big bug: alt tab, and you can never maximise again until you kill Fallout3.exe 2 possible solutions, Fake Fullscreen: how do I run Fallout_Fullscreen.exe with MO insted of Fallout3.exe? OneTweak: what does require FOSE mean? FOSE is a loader that also runs Fallout3 only with plugins, how does that work with MO?