The file extension is the first clue. stands for Compressed Hunks of Data . It is not a standard ROM file (like .zip or .bin ). It is a format developed by the MAME (Multiple Arcade Machine Emulator) project.
The Digital Legacy of Speed: Understanding "NASCAR Rumble -USA-.chd" NASCAR Rumble -USA-.chd
150 BPM (Fast, Driving Rock) Style: High-Energy Symphonic Rock / Arcade Racer The file extension is the first clue
: Use the password C9P5AU8NAA to unlock everything through the Pro level. NASCAR Rumble -USA-.chd