. While most ROMs (over 99%) remain compatible between minor versions like 0.250 and 0.251, even small changes in the MAME source code can make a specific game's ROM files unplayable if they don't match the version's requirements.
: ROMs must remain in their original ZIP or 7-Zip format; do not unzip individual game files before placing them in the emulator's roms folder.
With 0.250, the developers continued their trend of purging bad dumps and placeholder files. This means that many ROM sets (collections of game files) changed structure.
When downloading a collection, you will encounter three types of files: