DLed a fresh copy of Mugen, DLed the AoF archive, and got
Error message: Error loading TitleBGCan't open the SFF right now because I haven't DLed any viewer on this comp, but you might be missing something in the system, or maybe a misplaced/misreferenced file in the data I presume.
Error loading system data: data/mugen1/system.def
Library error message: Sprite doesn't exist: 5,0
Error in [TitleBG 1]
If I struggled to the end of my determination, to the end of my way of life with my followers, if the result is ruin, then this ruin is inevitable. Grieve. Shed tears. But you cannot regret.