you can't edit CFG files.
Actually, you CAN edit cfg files,
IF you use mame 0.85 or after. So get a current mame and take a look. It's in an xml file format, pretty easy to understand.
EasyEmu just added some info (
direct link to the best, ATM, page). MameFAQ has
a little info, too, but not much.
Of course, you can't hand edit on pre 0.84 mames, like it looks you're using.