In the world of emulation, MAME uses a format called (Compressed Hunk of Data) to store these large disk images. To play MvC2, you need both: The ROM (ZIP file): Contains the basic startup code.
To play Marvel Vs Capcom 2 on MAME, you need two main things: the MAME software itself and the game data, which for Marvel Vs Capcom 2, comes in the form of a CHD (Compressed Hard Drive) file. Marvel Vs Capcom 2 Chd Download Mame