Arcade ROMs often share common files. For example, Street Fighter II and Street Fighter II: Champion Edition might share the same background music files.
FBNeo generally prefers Non-Merged or Split sets. If you have a "Merged" file and the emulator expects a "Split" one, or vice versa, you will get an "Unknown" error. romset+is+unknown+fbneo+fixed+free
Open your emulator and look for the version number (usually displayed at the top or in the "Help" > "About" section). You need to know which "set" you need. Arcade ROMs often share common files
Because we cannot host ROM links here due to copyright, you must learn the lingua franca of emulation. Search for "FBNeo 1.0.0.3 ROM Set" or "FBNeo Split Set" on archive sites. FBNeo generally prefers Non-Merged or Split sets
If you are trying to play a clone (like a regional variant of a game) but you don't have the main "Parent" ROM in the same folder, FBNeo cannot fill in the missing data.
FBNeo provides .dat files on their official website. These are blueprints that tell you exactly what files need to be inside a game ZIP.