I made a game with TGF1 that used the extension "dmc2.gox".
Unfortunately today when I want to reopen this game with MMF2, I can't because "Can't find extension dmc2.mfx" error.
I copy dmc2.gox (renamed dmc2.mfx, because I can't find any link to download it ...) in several folders of MMF2, but MMF2 don't find it.
You need the MMF1 version of the DMC2 object to open it in MMF2. It needs to be in the 'MMF1' folder inside the 'Extension' folder.
or
Do you still have TGF1?
you can always open it in that and delete all of the DMC2 events. You wont need to actually use it in MMF2 because that can play mod music without any music objects.