The system already has numerous Neo games on it (Magical Drop 2, Fatal Fury 2, Last Resort, Money Puzzle Exchanger, Cyber Lip, Robo Army, Sengoku 1 & 2, etc.) I added KOF '98 & Pulstar yesterday and neither of those would boot either. I haven't tried them all yet, but the preinstalled Neo ones I did try all worked except for Samurai Shodown 4. There's got to be a bios file already on there, or none of the Neo games would work at all.
I looked for hidden files on it with my laptop, but, didn't come up with anything. There's just one games folder, where all the preinstalled NES and GBA ROMs can be found, but none of the NeoGeo & CPS1/2 games. Maybe they're built right into the hardware?
I'll try downloading some bios files and putting those in the new folders I created for MAME and NeoGeo zipped ROMs.