Yeah that DAT file is what I am looking for. My front end has the option to exclude non-working ROMs and even has a category for CHD games so it is filtering it somehow. I may ask on the front end site. Come to think of it I have a list of the games that I can see in the GUI (about 120 CHD games). But I need something to map the games full name to the file name. Like Gauntlet Legends is one of the games that works. Does one of the mame dat files map the title to the file name like glegends.zip (just guessing). I just want to put the working CHDs on my portable and delete the rest.