Thank you for the replys but im not over thinking this i want to understand it , so let ke put it to you another way , what is the best way to put to the most complete rom pkg together that has the most games that work , ie chds , mame non metged and bios , or chds merged roms and bios or chds split roms and bios ? And do you put them all in sub folders in roms ,( cause if i put them together. They try to overwrite each other ) space dont matter to me i have a 4 tb drive , just trying to put together the most complete set