For now, i wouldn't spend too much time getting involved with that, i would just concentrate on the basics. For some reason, this is becoming more and more of a problem lately, not sure why, so i will outline for you and anyone who is just getting into MAME as a hobby. Firstly, everything must match! Running MAME 154? You MUST have a 154 romset. Period. Have a 156 romset? You MUST compile a 156 MAME.exe. You should never mix versions when it comes to MAME. It is not like a regular emulator, which is why it doesn't get treated as one in GX. Whenever you can, you should also match all support files in the same manner, so if you have MAME .154, you will need mameinfo, history, catver, etc version 154 to match. I know it seems unforgiving, but MAME is unforgiving - It wants everything to match and you should strive to make that happen. If not then it's probably not realistically going to work for you, at least not flawlessly which i'm sure you want