Lachy5

Hi guys, I've just bought a copy of Vice city pc, thought it would be good to bring back some old memories and mod the game to make it a different experience aswell. When i go to replace the .dff and .txd files in imgtool it wont do it and says that the file I'm trying to replace is too big. I have been modding San Andreas for a while and have not had this problem. anyone know what the issue might be??