if it was a bad rom dump then there is nothing you can do the rom is pretty much screwed i think you gotta try dl'in from somewhere else. as for dat files just do a google search for what set you need, like for mame or fbaxxx or kawa or whatever. if you use romcenter the mame dats come included when you first dl it. dats can only fix a game if it can be fixed tho, some roms are just screwed. i suggest dling the rom again