Yes, only encrypted romsets use 2 M1 roms which help the emulatores dercrypt encrypted rom sets. See example of KOF2k2: System: NEO RomName: kof2002 Game: The King of Fighters 2002 (encrypted) [Program] 265-p1.bin,0,100000,9EDE7323,0 265-p2.bin,100000,400000,327266B8,0 [Text] [Z80] 265-m1d.bin,0,20000,AB9D360E,0 [samples] 265-v1d.bin,0,400000,13D98607,0 265-v2d.bin,400000,400000,9CF74677,0 265-v3d.bin,800000,400000,8E9448B5,0 265-v4d.bin,C00000,400000,067271B5,0 [Graphics] 265-c1.bin,0,800000,2B65A656,0 265-c2.bin,1,800000,ADF18983,0 265-c3.bin,1000000,800000,875E9FD7,0 265-c4.bin,1000001,800000,2DA13947,0 265-c5.bin,2000000,800000,61BD165D,0 265-c6.bin,2000001,800000,03FDD1EB,0 265-c7.bin,3000000,800000,1A2749D8,0 265-c8.bin,3000001,800000,AB0BB549,0 [system] CartridgeID: 265 GfxCrypt: 2 GfxKey: EC ButLayout: 9 Fix: 1E %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% System: NEO RomName: KOF2K2ND Game: The King of Fighters 2002 - Challenge To Ultimate Battle (fully decrypted) [Program] kof2k2_p1.rom,0,100000,0,0 kof2k2_p2.rom,100000,400000,0,0 [Text] kof2k2_s1.rom,0,20000,0,0 [Z80] kof2k2_m1.rom,0,20000,0,0 [samples] kof2k2_v1.rom,0,400000,0,0 kof2k2_v2.rom,400000,400000,0,0 kof2k2_v3.rom,800000,400000,0,0 kof2k2_v4.rom,C00000,400000,0,0 [Graphics] kof2k2_c1.rom,0,800000,0,0 kof2k2_c2.rom,1,800000,0,0 kof2k2_c3.rom,1000000,800000,0,0 kof2k2_c4.rom,1000001,800000,0,0 kof2k2_c5.rom,2000000,800000,0,0 kof2k2_c6.rom,2000001,800000,0,0 kof2k2_c7.rom,3000000,800000,0,0 kof2k2_c8.rom,3000001,800000,0,0 [system] CartridgeID: 265 GfxCrypt: 0 GfxKey: 0 ButLayout: 9 Fix: C Also in the encrypted set, you'll notice that only the m1d and V-d roms are listed in the dat, but the regular m1, and the merged v-rom sets are not listed but present in the romset. The D versions of the roms are from old romsets which help like that of a cps2 rom, basically decrypt them. so if KOF2k3's C roms are encrypted, you'll have to run them with an encrypted set. And likewise if the rom is decrypted.